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PubMed1997

Cellular recombination pathways and viral terminal repeat hairpin structures are sufficient for adeno-associated virus integration in vivo and in vitro.

The human parvovirus adeno-associated virus (AAV) is unique in its ability to target viral integration to a specific site on chromosome 19 (ch-19). Recombinant AAV (rAAV) vectors retain the ability to integrate but have apparently lost this ability to target. In this report, we characterize the terminal-repeat-mediated integration for wild-type (wt), rAAV, and in vitro systems to gain a better understanding of these differences. Cell lines latent for either wt or rAAV were characterized by a variety of techniques, including PCR, Southern hybridization, and fluorescence in situ hybridization analysis. More than 40 AAV-rAAV integration junctions were cloned, sequenced, and then subjected to comparison and analysis. In both immortalized and normal diploid human cells, wt AAV targeted integration to ch-19. Integrated provirus structures consisted of head-to-tail tandem arrays with the majority of the junction sequences involving the AAV inverted terminal repeats (ITRs). No complete viral ITRs were directly observed. In some examples, the AAV p5 promoter sequence was found to be fused at the virus-cell junction. Data from dot blot analysis of PCR products were consistent with the occurrence of inversions of genomic and/or viral DNA sequences at the wt integration site. Unlike wt provirus junctions, rAAV provirus junctions mapped to a subset of non-ch-19 sequences. Southern analysis supported the integration of proviruses from two independent cell lines at the same locus on ch-2. In addition, provirus terminal repeat sequences existed in both the flip and flop orientations, with microhomology evident at the junctions. In all cases with the exception of the ITRs, the vector integrated intact. rAAV junction sequence data were consistent with the occurrence of genomic rearrangement by deletion and/or rearrangement-translocation at the integration locus. Finally, junctions formed in an in vitro system between several AAV substrates and the ch-19 target site were isolated and characterized. Linear AAV substrates typically utilized the end of the virus DNA substrate as the point of integration, whereas products derived from AAV terminal repeat hairpin structures in the presence or absence of Rep protein resembled AAV-ch-19 junctions generated in vivo. These results describing wt AAV, rAAV, and in vitro integration junctions suggest that the viral integration event itself is mediated by terminal repeat hairpin structures via nonviral cellular recombination pathways, with specificity for ch-19 in vivo requiring additional viral components. These studies should have an important impact on the use of rAAV vectors in human gene therapy.

Base Sequence↗

PubMed2006

Karyotypic characterization and genomic organization of the 5S rDNA in Erpetoichthys calabaricus (Osteichthyes, Polypteridae).

Polypterids are a group of Osteichthyan fish whose evolutionary relationships with closer basal ray-finned and lobe-finned fish have been disputed since their discovery. Very little is known about the evolutive karyology in the whole Polypteriformes group. In order to fill this gap, a cytogenetic analysis of Erpetoichthys calabaricus species was performed, using both classical and molecular techniques. Karyotype structure (2n = 36; FN = 72), chromosome location of telomeric sequences (TTAGGG)n and ribosomal 5S and 18S rRNA genes were examined in twenty specimens of E. calabaricus by using Ag-NOR, classical C-banding, sequential CMA3/4',6-diaminidino-2-phenylindole (DAPI) staining and fluorescent in situ hybridization (FISH). CMA3 marked all centromerical and some (no. 1 and no. 15) telomeric regions. Staining with Ag-NOR and CMA3 showed the presence of two NORs on the p arm of the chromosome pair no. 1. Hybridization with telomeric probes (TTAGGG)n showed signals at the end of all chromosomes. 5S rDNA was cloned and sequenced. After the alignment, the 5S rRNA sequences revealed an organization made up of two different classes of tandem arrays (type I and type II). FISH with 5S rDNA marked the telomeric regions of the small chromosome pair no. 15, while FISH with 18S rDNA marked the telomeric region of the pair no. 1. The results obtained were compared with cariological data on closer species now available in literature.

Animals↗

PubMed2003

Long-range silencing and position effects at telomeres and centromeres: parallels and differences.

Most of the human genome is compacted into heterochromatin, a form that encompasses multiple forms of inactive chromatin structure. Transcriptional silencing mechanisms in budding and fission yeasts have provided genetically tractable models for understanding heritably repressed chromatin. These silent domains are typically found in regions of repetitive DNA, that is, either adjacent to centromeres or telomeres or within the tandemly repeated ribosomal DNA array. Here we address the mechanisms of centromeric, telomeric and locus-specific gene silencing, comparing simple and complex animals with yeast. Some aspects are universally shared, such as histone-tail modifications, while others are unique to either centromeres or telomeres. These may reflect roles for heterochromatin in other chromosomal functions, like kinetochore attachment and DNA ends protection.

Animals↗

PubMed2006

Inhibition of poly(ADP-ribose)polymerase does not affect the recombination events in CHO xrs6 and wild type cells.

Activation of poly (ADP-ribose) polymerase -1 (PARP-1) is an early DNA damage response event that, together with phosphorylation of p53, prompts various cellular functions important in the maintenance of the genome stability. In mammalian cells, DSB are repaired by nonhomologous end-joining (NHEJ) and by homologous recombination (HR). To investigate the role of PARP-1 in HR, CHO-K1 wild type and xrs-6 mutant cell line were transfected with pLrec plasmids which carry two nonfunctional copies of the beta-galactosidase (lacZ) gene in a tandem array. In result of HR they can give rise to a functional copy of beta-galactosidase. To test whether PARP-1 affects the frequency of spontaneous and induced recombination repair, we treated CHO-K1 and xrs6 clones carrying chromosomally integrated pLrec with the PARP-1 inhibitor 3-aminobenzamide (3AB). Our results show that the spontaneous homologous intrachromosomal recombination frequency between the two lacZ copies was almost two orders of magnitude higher in xrs6 cells than in CHO-K1 cells, but that it was not affected by 3AB treatment. Induction of DNA damage by irradiation or electroporation of restriction enzymes did not significantly increase the recombination frequency. Furthermore, in both the cell lines, the effect of PARP-1 inhibition on DSB repair was examined using the neutral comet assay. There was no effect of 3AB treatment on DSB rejoining after 10 Gy irradiation. The results presented support the conclusion that PARP-1 is not directly involved in HR.

Animals↗

PubMed1996

High-resolution mapping of repetitive DNA by in situ hybridization: molecular and chromosomal features of prominent dispersed and discretely localized DNA families from the wild beet species Beta procumbens.

Members of three prominent DNA families of Beta procumbens have been isolated as Sau3A repeats. Two families consisting of repeats of about 158 bp and 312 bp are organized as satellite DNAs (Sau3A satellites I and II), whereas the third family with a repeat length of 202 bp is interspersed throughout the genome. Multi-colour flourescence in situ hybridization was used for physical mapping of the DNA families, and has shown that these tandemly organized families occur in large heterochromatic and DAPI positive blocks. The Sau3A satellite I hybridized exclusively around or near the centromeres of 10, 11 or 12 chromosomes. The Sau3A satellite family I showed high intraspecific variability and high-resolution physical mapping was performed on pachytene chromosomes using differentially labelled repeats. The physical order of satellite subfamily arrays along a chromosome was visualized and provided evidence that large arrays of plant satellite repeats are not contiguous and consist of distinct subfamily domains. Re-hybridization of a heterologous rRNA probe to mitotic metaphase chromosomes revealed that the 18S-5.8S-25S rRNA genes are located at subterminal position on one chromosome pair missing repeat clusters of the Sau3A satellite family I. It is known that arrays of Sau3A satellite I repeats are tightly linked to a nematode (Heterodera schachtii) resistance gene and our results show that the gene might be located close to the centromere. Large arrays of the Sau3A satellite II were found in centromeric regions of 16 chromosomes and, in addition, a considerable interspersion of repeats over all chromosomes was observed. The family of interspersed 202 bp repeats is uniformly distributed over all chromosomes and largely excluded from the rRNA gene cluster but shows local amplification in some regions. Southern hybridization has shown that all three families are specific for genomes of the section Procumbentes of the genus Beta.

Base Sequence↗

PubMed2006

Analyses of carnivore microsatellites and their intimate association with tRNA-derived SINEs.

BACKGROUND: The popularity of microsatellites has greatly increased in the last decade on account of their many applications. However, little is currently understood about the factors that influence their genesis and distribution among and within species genomes. In this work, we analyzed carnivore microsatellite clones from GenBank to study their association with interspersed repeats and elucidate the role of the latter in microsatellite genesis and distribution. RESULTS: We constructed a comprehensive carnivore microsatellite database comprising 1236 clones from GenBank. Thirty-three species of 11 out of 12 carnivore families were represented, although two distantly related species, the domestic dog and cat, were clearly overrepresented. Of these clones, 330 contained tRNALys-derived SINEs and 357 contained other interspersed repeats. Our rough estimates of tRNA SINE copies per haploid genome were much higher than published ones. Our results also revealed a distinct juxtaposition of AG and A-rich repeats and tRNALys-derived SINEs suggesting their coevolution. Both microsatellites arose repeatedly in two regions of the interspersed repeat. Moreover, microsatellites associated with tRNALys-derived SINEs showed the highest complexity and less potential instability. CONCLUSION: Our results suggest that tRNALys-derived SINEs are a significant source for microsatellite generation in carnivores, especially for AG and A-rich repeat motifs. These observations indicate two modes of microsatellite generation: the expansion and variation of pre-existing tandem repeats and the conversion of sequences with high cryptic simplicity into a repeat array; mechanisms which are not specific to tRNALys-derived SINEs. Microsatellite and interspersed repeat coevolution could also explain different distribution of repeat types among and within species genomes.Finally, due to their higher complexity and lower potential informative content of microsatellites associated with tRNALys-derived SINEs, we recommend avoiding their use as genetic markers.

Animals↗

PubMed2005

Evolutionary turnover of two pBuM satellite DNA subfamilies in the Drosophila buzzatii species cluster (repleta group): from alpha to alpha/beta arrays.

The pBuM satellite DNA family was studied in seven Drosophila species from the buzzatii cluster (within the large Drosophila repleta group). The pBuM repeats are slightly AT-rich and show high levels of intraspecific sequence homogeneity. The pBuM family can be divided into two subfamilies. The pBuM-1 subfamily consists of tandemly arranged repetition units of approximately 190 bp, termed alpha. Alpha repeats were found in a high copy number in the genome of D. buzzatii, D. serido and D. antonietae. The pBuM-2 subfamily consists of tandemly arranged repetition units of 370 bp. Its origin is explained by an insertion of an approximately 180 bp foreign sequence (termed beta) in an alpha basic repeat unit, with subsequent homogenization/amplification events increasing its frequency. Alpha/beta repeats were found in a high copy number in the genome of D. serido, D. antonietae, D. seriema and D. gouveai. pBuM sequences were not detected in D. koepferae and D. borborema by hybridization experiments. The nucleotide analysis of 74 pBuM repeats revealed that apart from the beta insertion event, the evolution of the pBuM family has proceeded in a gradual fashion, mainly through accumulation and horizontal spread of nucleotide substitutions. Moreover, the data also indicate a faster evolutionary rate for the pBuM-2 subfamily than the pBuM-1 subfamily. Members of both subfamilies display a greater intraspecific than interspecific homogeneity, indicating a concerted mode of pBuM evolution. A scenario to explain the evolution of both satDNA subfamilies in the seven Drosophila species from the buzzatii cluster is proposed.

Animals↗

PubMed2002

Identification of tandemly-repeated C/D snoRNA genes at the imprinted human 14q32 domain reminiscent of those at the Prader-Willi/Angelman syndrome region.

A human imprinted domain at 14q32 contains two co-expressed and reciprocally imprinted genes, DLK1 and GTL2, which are expressed from the paternally and maternally inherited alleles, respectively. We have previously shown that another imprinted locus, on human 15q11-q13, contains a large number of tandemly repeated C/D small nucleolar RNA genes (or C/D snoRNAs) only expressed from the paternal allele. Here we show that the region downstream from the GTL2 gene is also characterized by a transcription unit spanning many repeated intron-encoded C/D snoRNA genes, most of them arranged into two tandem arrays of 31 and 9 copies. Intriguingly, these snoRNAs depart from previously reported rRNA or snRNA methylation guides by their tissue-specific expression and by their lack of complementarity to rRNA or snRNA within their sequences. Analysis of the orthologous region in the mouse shows that the previously reported maternally expressed Rian gene, located downstream of Gtl2 on the distal 12 chromosome, encodes at least nine C/D snoRNAs. Through a systematic search in rodents, we could identify other C/D snoRNA genes in this domain. All snoRNAs identified on mouse distal 12 are brain-specific and only expressed from the maternally inherited allele. The human imprinted 14q32 domain therefore shares common genomic features with the imprinted 15q11-q13 loci. This link between tandemly repeated C/D snoRNA genes and genomic imprinting suggests a role for these snoRNAs and/or their host non-coding RNA genes in the evolution and/or mechanism of the epigenetic imprinting process.

Angelman Syndrome↗

PubMed1982

Colobus type C virus: molecular cloning of unintegrated viral DNA and characterization of the endogenous viral genomes of Colobus.

The unintegrated viral DNA intermediates of colobus type C virus (CPC-1) were isolated from infected human cells that were permissive for viral growth. There were two major species of DNA, linear molecules with two copies of the long terminal repeat and relaxed circles containing only a single long terminal repeat. In addition, there was a minor species (approximately 10%) composed of relaxed circles with two copies of the long terminal repeat. A restriction endonuclease map of the unintegrated DNA was constructed. The three EcoRI fragments of circular CPC-1 DNA were cloned in the EcoRI site of lambda gtWES . lambda B and then subcloned in the EcoRI site of pBR322. Using these subgenomic fragments as probes, we have characterized the endogenous viral sequences found in colobus cellular DNA. They are not organized in tandem arrays, as is the case in some other gene families. The majority of sequences detected in cellular DNA have the same map as the CPC-1 unintegrated DNA at 17 of 18 restriction endonuclease sites. There are, however, other sequences that are present in multiple copies and do not correspond to the CPC-1 map. They do not contain CPC-1 sequences either in an altered form or fused to common nonviral sequences. Instead, they appear to be derived from a distinct family of sequences that is substantially diverged from the CPC-1 family. This second family of sequences, CPC-2, is also different from the sequences related to baboon endogenous type C virus that forms a third family of virus-related sequences in the colobus genome.

Animals↗

PubMed1998

Isolation and characterization of human SGT and identification of homologues in Saccharomyces cerevisiae and Caenorhabditis elegans.

We have recently isolated a rat cDNA encoding a novel cellular protein able to interact with the major nonstructural protein NS1 of parvovirus H-1 and have termed this protein SGT, for small glutamine-rich tetratricopeptide repeat (TPR)-containing protein. Here we report the isolation of a cDNA from human placenta encoding the human homologue, human SGT. SGT from rat and human contain 314 and 313 amino acids, respectively, and share 91% sequence identity at the protein level. The highest degree of similarity is present within the central region containing three TPR motifs in tandem array. The similarities, however, also extend beyond this region. Human SGTtranscript was found to be ubiquitously present in all human tissues tested. By fluorescence in situ hybridization analysis we have mapped the human gene to chromosome 19p13. The SGT-coding sequences are evolutionarily conserved, since we could identify genes encoding proteins of similar size and structure in the genomes of Saccharomyces cerevisiae and Caenorhabditis elegans.

Amino Acid Sequence↗

PubMed1985

Drosophila P element integration in the mouse.

A recombinant plasmid containing the Drosophila melanogaster P element transposon was microinjected into mouse zygotes. Dot-blot analysis indicated that one of the newborns contained a single copy of the microinjected DNA per haploid mouse genome equivalent; two other newborns had integrated multiple copies of the P element construct. Southern mapping revealed that the entire plasmid, including both pBR322 sequences and P element sequences, had integrated in each of the three animals. In the two mice carrying multiple copies of the microinjected DNA, the copies appear to be linked in a tandem head-to-tail array. Therefore, in each of the three newborns integration of P element sequences has occurred by a mechanism which is distinct from that observed when the same plasmid is injected into Drosophila embryos. Analysis of DNA from the offspring of one of the transgenic mice showed no indication of transposition of P element sequences.

Animals↗

PubMed2005

Rapid and repeatable elimination of a parental genome-specific DNA repeat (pGc1R-1a) in newly synthesized wheat allopolyploids.

Recent work in the Triticum-Aegilops complex demonstrates that allopolyploidization is associated with an array of changes in low-copy coding and noncoding sequences. Nevertheless, the behavior and fate of repetitive DNA elements that constitute the bulk of nuclear DNA of these plant species is less clear following allopolyploidy. To gain further insight into the genomic events that accompany allopolyploid formation, we investigated fluorescence in situ hybridization (FISH) patterns of a parental-specific, tandem DNA repeat (pGc1R-1) on three sets of newly synthesized amphiploids with different parental species. It was found that drastic physical elimination of pGc1R-1 copies occurred in all three amphiploids in early generations. DNA gel-blot analysis confirmed the FISH data and estimates indicated that approximately 70-90% of the copies of the pGc1R-1 repeat family were eliminated from the amphiploids by the second to third selfed generations. Thus, allopolyploidy in Triticum-Aegilops can be accompanied by rapid and extensive elimination of parental-specific repetitive DNA sequences, which presumably play a role in the initial stabilization of the nascent amphiploid plants.

Electrophoresis↗

PubMed1999

Comparative sequence analysis of human minisatellites showing meiotic repeat instability.

The highly variable human minisatellites MS32 (D1S8), MS31A (D7S21), and CEB1 (D2S90) all show recombination-based repeat instability restricted to the germline. Mutation usually results in polar interallelic conversion or occasionally in crossovers, which, at MS32 at least, extend into DNA flanking the repeat array, defining a localized recombination hotspot and suggesting that cis-acting elements in flanking DNA can influence repeat instability. Therefore, comparative sequence analysis was performed to search for common flanking elements associated with these unstable loci. All three minisatellites are located in GC-rich DNA abundant in dispersed and tandem repetitive elements. There were no significant sequence similarities between different loci upstream of the unstable end of the repeat array. Only one of the three loci showed clear evidence for putative coding sequences near the minisatellite. No consistent patterns of thermal stability or DNA secondary structure were shared by DNA flanking these loci. This work extends previous data on the genomic environment of minisatellites. In addition, this work suggests that recombinational activity is not controlled by primary or secondary characteristics of the DNA sequence flanking the repeat array and is not obviously associated with gene promoters as seen in yeast.

CpG Islands↗

PubMed1989

Chromosome-specific alpha satellite DNA from the centromere of human chromosome 16.

To examine the molecular organization of DNA sequences located in the centromeric region of human chromosome 16 we have isolated and characterized a chromosome 16-specific member of the alpha satellite DNA family. The probe obtained is specific for the centromere of chromosome 16 by somatic cell hybrid analysis and by fluorescence in situ hybridization and allows detection of specific hybridizing domains in interphase nuclei. Nucleotide sequence analysis indicates that this class of chromosome 16 alpha satellite (D16Z2) is organized as a series of diverged 340-bp dimers arranged in a tandem array of 1.7-kb higher-order repeat units. As measured by pulsed-field gel electrophoresis, the total D16Z2 array spans approximately 1,400-2,000 kb of centromeric DNA. These sequences are highly polymorphic, both by conventional agarose-gel electrophoresis and by pulsed-field gel electrophoresis. Investigation of this family of alpha satellite should facilitate the further genomic, cytogenetic, and genetic analysis of chromosome 16.

Centromere↗

PubMed2005

From genome to vaccines for leishmaniasis: screening 100 novel vaccine candidates against murine Leishmania major infection.

The genomic sequence of Leishmania major provides a rich source of vaccine candidates. One hundred randomly selected amastigote-expressed genes were screened as DNA vaccines, and efficacy determined following high-dose L. major footpad challenge in BALB/c mice. Fourteen protective novel vaccine candidates were identified; seven vaccines exacerbated disease. There were no differences in the number of predicted MHC H-2d class I or II epitopes mapping to protective versus exacerbatory antigens. A proportion of both protective (7/14; 50%) and exacerbatory (4/7; 57%) proteins showed short (8- to 18-mer) 100% amino acid sequence identities to human, mouse or gut flora proteins. A high proportion of these (4/7 protective; 3/4 exacerbatory) showed full or partial overlap with RANKPEP-predicted H-2d classes I and II epitopes. Our data suggest, therefore, that there may be little difference between antigens/epitopes that drive regulatory versus effector CD4 T cell populations. The best novel protective antigen was an amastin-like gene that maps to a 17-gene tandem array on Leishmania chromosome 8 and is closely related to 37 other amastin-like genes. Two ribosomal proteins, a V-ATPase subunit, and a dynein light chain orthologue were the only other protective genes with putative functions.

Animals↗

PubMed2000

The Trypanosoma cruzi genome contains ion motive ATPase genes which closely resemble Leishmania proton pumps.

DNA fragments homologous to members of the family of P-type ion-motive ATPases were identified in Trypanosoma cruzi by polymerase chain reaction (PCR) amplification. The sequence of one fragment, which closely resembled (87% identity) the tandemly linked proton pumps in Leishmania, was used to characterize the H(+)-ATPase genes in T. cruzi. The T. cruzi proton pump locus contains four tandemly repeated genes (TCH1-4) separated by 1.1 kb intergenic regions. The nucleotide sequence of one cloned gene of the tandem array contains a 2775 nt open reading frame encoding a predicted 101908-Da protein of 925 amino acids. The TCH genes are expressed as 3.8 and 4.9 kb polyadenylated transcripts in the epimastigote stage; expression of both transcripts is reduced in metacyclic trypomastigotes. Results of 5' and 3' RACE transcript mapping indicate that the 3.8 kb message is generated from within the tandemly repeated locus. The 3.8 kb TCH transcript has the T. cruzi mini-exon appended to a short (40 nt) 5' untranslated region (UTR) and has a 927 nt 3' UTR. The full peptide sequence of the T. cruzi proton pump is 80% identical to the Leishmania pump but lacks the extended carboxyl tail present in the Leishmania ATPase. An antibody that recognizes the 110-kDa Leishmania donovani proton pump cross-reacts with a 100-kDa protein in lysates of T. cruzi epimastigotes.

Amino Acid Sequence↗

PubMed1994

Synthetic DNA probes to identify members of the Anopheles gambiae complex and to distinguish the two major vectors of malaria within the complex, An. gambiae s.s. and An. arabiensis.

Two cloned DNA sequences, lambda C10 and lambda G12, have been isolated from a female Anopheles gambiae sensu stricto genomic DNA library in lambda EMBL4. The lambda C10 clone hybridized with equal intensity to all five of the six species in the An. gambiae Giles complex tested and was therefore suitable for use as a complex-specific clone. The lambda G12 clone was selected for its ability to distinguish the two major vectors of malaria within the complex, An. gambiae s.s. and An. arabiensis. Use of libraries consisting of only female DNA prevented the isolation of male-specific sequences. Southern blot analysis of the cloned DNA permitted the development of smaller Alu I subclones suitable for sequencing that still retained the original specificities and sensitivities of lambda C10 and lambda G12. Each clone was found to possess a series of repeated sequences in direct tandem array of 92-94 and 68 bases, respectively. A comparison of a number of copies of each of the repetitive sequences within the Alu I subclones enabled the definition of consensus sequences for the repetitive elements in lambda C10 and lambda G12. Based on these consensus sequences, two oligonucleotides of 21 and 23 bases designated pAngsl and pAngss were derived from lambda C10 and lambda G12, respectively. When tested as probes against DNA dot-blots and squash-blots of mosquito specimens, each oligonucleotide retained the same species specificity as the original clones from which they were derived. The nonradioactive, alkaline phosphatase-labeled pAngsl was able to detect as little as 1 ng of target genomic DNA by chemiluminescent detection in a 5-hr autoradiographic exposure. The pAngss probe could detect 5-10 ng of genomic DNA in similar assays. The new probes exhibit great potential for use in An. gambiae complex species identification because they provide both a means of distinguishing the two major vectors of malaria within the complex and of assessing the quality of squashed mosquito samples by providing a means of standardizing hybridization results.

Animals↗

PubMed2005

Modular evolution of egg case silk genes across orb-weaving spider superfamilies.

Spider silk proteins (fibroins) are renowned for their extraordinary mechanical properties and biomimetic potential. Despite extensive evolutionary, ecological, and industrial interest in these fibroins, only a fraction of the known silk types have been characterized at the molecular level. Here we report cDNA and genomic sequences of the fibroin TuSp1, which appears to be the major component of tubuliform gland silk, a fiber exclusively synthesized by female spiders for egg case construction. We obtained TuSp1 sequences from 12 spider species that represent the extremes of phylogenetic diversity within the Orbicularia (orb-weaver superfamilies, Araneoidea and Deinopoidea) and finer scale sampling within genera. TuSp1 encodes tandem arrays of an approximately 200-aa-long repeat unit and individual repeats are readily aligned, even among species that diverged >125 million years ago. Analyses of these repeats across species reveal the strong influence of concerted evolution, resulting in intragenic homogenization. However, deinopoid TuSp1 repeats also contain insertions of coding, minisatellite-like sequences, an apparent result of replication slippage and nonreciprocal recombination. Phylogenetic analyses of 37 spider fibroin sequences support the monophyly of TuSp1 within the spider fibroin gene family, consistent with a single origin of this ortholog group. The diversity of taxa and silks examined here confirms that repetitive architecture is a general feature of this gene family. Moreover, we show that TuSp1 provides a clear example of modular evolution across a range of phylogenetic levels.

Amino Acid Sequence↗