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D A Maslov

Publications and source records attributed to D A Maslov.

At least 19 recordsLinked to original sources
PubMed2000

Detection of the mitochondrially encoded cytochrome c oxidase subunit I in the trypanosomatid protozoan Leishmania tarentolae. Evidence for translation of unedited mRNA in the kinetoplast.

With the aim of identification of kinetoplast-encoded proteins we investigated the subunit composition of cytochrome c oxidase (respiratory complex IV) from kinetoplast mitochondria of the trypanosomatid protozoan Leishmania tarentolae. Eleven stoichiometric subunits were visible in Coomassie-stained, two-dimensional Blue Native/Tricine-SDS electrophoretic gels. Their partial amino acid sequences indicated that these polypeptides are nuclear-encoded. The mitochondrial subunit I was detected with the polyclonal antibodies against an internal region of this polypeptide. In two-dimensional (9 versus 14%) polyacrylamide glycine-SDS gels this subunit is found as a series of spots located off the main diagonal, a property that can be explained by abnormal electrophoretic migration and aggregation. In gels loaded with high amounts of the purified, enzymatically active oxidase, the subunit I spots could be visualized by staining. The determined N-terminal amino acid sequence of the putative monomeric subunit I (MFXLCLVCLSVS) matched with the predicted sequence, thus indicating that the corresponding kinetoplast unedited mRNA is translated into a functional protein.

Amino Acid Sequence↗
PubMed2000

Translation of the edited mRNA for cytochrome b in trypanosome mitochondria.

The type of RNA editing found in the kinetoplast-mitochondria of trypanosomes and related protozoa, involving uridylate insertions and deletions, creates translatable messenger RNAs (mRNAs) out of nonsense pre-edited RNAs by correcting encoded defects that vary from simple frameshifts to large "cryptic" regions. However, any evidence for translation of these mRNAs in the kinetoplast has been missing for decades. We identified a kinetoplast-encoded protein, apocytochrome b, whose mRNA is edited in the 5' region. The determined amino-terminal sequence of the protein coincides with the predicted sequence derived from the edited region, demonstrating that the cognate apocytochrome b mRNA is translated into a functional protein. This finding represents the first direct evidence for a functional translation system in the kinetoplasts.

Amino Acid Sequence↗
PubMed2000

Unexpectedly high variability of the histone H4 gene in Leishmania.

The sequence of the cDNA of the histone H4 gene of Leishmania tarentolae is reported herein. The predicted 100-amino-acid-long protein has the highest degree of identity with the histone H4 gene of L. infantum and shares with it a 5' region that shows a very low degree of identity with the corresponding region of histone H4 genes from other organisms. However, between these two genes is a 7.7% nucleotide difference that results in seven different amino acids, located in the 5', central, and 3' regions of the coding sequence. Such a divergence in the H4 gene, which is considered to be one of the most highly conserved genes, between closely related members of the genus Leishmania is unexpected and may reflect some unusual features of these important proteins in kinetoplastid flagellates.

Amino Acid Sequence↗
PubMed1999

Partial kinetoplast-mitochondrial gene organization and expression in the respiratory deficient plant trypanosomatid Phytomonas serpens.

In plant-dwelling trypanosomatids from the genus Phytomonas, mitochondrial functions, such as cytochrome mediated respiration, ATP production and Krebs cycle, are missing, and cell energetics is based on the glycolysis. Using Blue Native/Tricine-SDS two-dimensional gel electrophoretic analysis, we observed that mitochondrial respiratory Complexes III (cytochrome bc1) and IV (cytochrome c oxidase) were absent in Phytomonas serpens; however, Complex V (ATPase) was present. A deletion of the genes for cytochrome c oxidase subunit III (COIII) and apocytochrome b (Cyb) was identified within the 6234 bp sequenced region of the 31 kb maxicircle kinetoplast DNA. Genes, found in this region, include 12S and 9S ribosomal RNAs, subunits 7, 8 and 9 of NADH dehydrogenase (ND7, ND8 and ND9) and subunit 6 of ATPase (A6 or MURF4), as well as the genes (MURF1, MURF5 and G3) with unknown function. Most genes are actively transcribed and some mRNAs are edited. Fully edited mRNAs for A6 and G3 were abundant, while edited ND7 transcripts were rare, and only partially edited and pre-edited transcripts for ND8 were detected. The data show that the mitochondrial genome of P. serpens is functional, although its functions may be limited to expressing the ATPase and, possibly, NADH dehydrogenase complexes.

Adenosine Triphosphatases↗
PubMed1999

Phylogenetic affinities of Diplonema within the Euglenozoa as inferred from the SSU rRNA gene and partial COI protein sequences.

In order to shed light on the phylogenetic position of diplonemids within the phylum Euglenozoa, we have sequenced small subunit rRNA (SSU rRNA) genes from Diplonema (syn. Isonema) papillatum and Diplonema sp. We have also analyzed a partial sequence of the mitochondrial gene for cytochrome c oxidase subunit I from D. papillatum. With both markers, the maximum likelihood method favored a closer grouping of diplonemids with kinetoplastids, while the parsimony and distance suggested a closer relationship of diplonemids with euglenoids. In each case, the differences between the best tree and the alternative trees were small. The frequency of codon usage in the partial D. papillatum COI was different from both related groups; however, as is the case in kinetoplastids but not in Euglena, both the non-canonical UGA codon and the canonical UGG codon were used to encode tryptophan in Diplonema.

Amino Acid Sequence↗
PubMed1998

Demonstration of mRNA editing and localization of guide RNA genes in kinetoplast-mitochondria of the plant trypanosomatid Phytomonas serpens.

Maxicircle molecules of kDNA in several isolates of Phytomonas were detected by hybridization with the 12S rRNA gene probe from Leishmania tarentolae. The estimated size of maxicircles is isolate-specific and varies from 27 to 36 kb. Fully edited and polyadenylated mRNA for kinetoplast-encoded ribosomal protein S12 (RPS12) was found in the steady-state kinetoplast RNA isolated from Phytomonas serpens strain 1G. Two minicircles (1.45 kb) from this strain were also sequenced. Each minicircle contains two 120 bp conserved regions positioned 180 degrees apart, a region enriched with G and T bases and a variable region. One minicircle encodes a gRNA for the first block of editing of RPSl2 mRNA, and the other encodes a gRNA with unknown function. A gRNA gene for the second block of RPSl2 was found on a minicircle sequenced previously. On each minicircle, a gRNA gene is located in the variable region in a similar position and orientation with respect to the conserved regions.

Amino Acid Sequence↗
PubMed1998

U-insertion/deletion Edited Sequence Database.

Uridine insertion/deletion RNA editing is a post-transcriptional RNA modification occurring in the mitochondria of kinetoplastid protozoa. The U-insertion/deletion Edited Sequence Database is a compilation of mitochondrial genes and edited mRNAs from five kinetoplastid species. It contains separate files with the DNA, mRNA (both unedited and edited) and predicted protein sequences, as well as alignments of the Leishmania tarentolae and Trypanosoma brucei protein sequences from edited and unedited genes. The sequence files are in GCG format. A 'map' sequence file showing the location of U-deletions, U-insertions and the translated amino acid sequences is also provided for each gene. Genomic maps for each species are also provided with clickable genes, including maxicircle-encoded gRNAs. Sets of aligned nuclear rRNA sequences from kinetoplastid protozoa are also provided, which were used for phylogenetic reconstructions in an analysis of the origin of RNA editing. The database is available through the World Wide Web as an HTML document at the URLhttp://www.lifesci.ucla.edu/RNA/trypanosome/ database.html

Animals↗
PubMed1997

Analysis of ribosomal RNA genes suggests that trypanosomes are monophyletic.

To further investigate the phylogeny of protozoa from the order Kinetoplastida we have sequenced the small subunit (SSU) and a portion of the large subunit (LSU) nuclear rRNA genes. The SSU and LSU sequences were determined from a lizard trypanosome, Trypanosoma scelopori and a bodonid, Rhynchobodo sp., and the LSU sequences were determined from an insect trypanosomatid, Crithidia oncopelti, and a bodonid, Dimastigella trypaniformis. Contrary to previous results, in which trypanosomes were found to be paraphyletic, with Trypanosoma brucei representing the earliest-diverging lineage, we have now found evidence for the monophyly of trypanosomes. Addition of new taxa which subdivide long branches (such as that of T. brucei) have helped to identify homoplasies responsible for the paraphyletic trees in previous studies. Although the monophyly of the trypanosome clade is supported in the bootstrap analyses for maximum likelihood at 97% and maximum parsimony at 92%, there is only a small difference in ln-likelihood value or tree length between the most optimal monophyletic tree and the best suboptimal paraphyletic tree. Within the trypanosomatid subtree, the clade of trypanosomes is a sister group to the monophyletic clade of the nontrypanosome genera. Different groups of trypanosomes group on the tree according to their mode of transmission. This suggests that the adaptation to invertebrate vectors plays a more important role in the trypanosome evolution than the adaptation to vertebrate hosts.

Animals↗
PubMed1996

Detection and identification of human pathogenic Leishmania and Trypanosoma species by hybridization of PCR-amplified mini-exon repeats.

A single pair of PCR primers within a conserved region of the mini-exon repeat was used to amplify the repeats from 10 species of pathogenic Leishmania belonging to four major clinical groups and also from three species of Trypanosoma. Oligonucleotide hybridization probes for the detection and identification of the PCR-amplified repeats were constructed from alignments of mini-exon intron and intergenic sequences. The probes generated from mini-exon intergenic regions of the L. (V.) braziliensis, L. (L.) donovani, and L. (L.) mexicana species hybridized specifically to their cognate groups without discriminating between the species within the groups. The probes for L. (L.) major and L. (L.) aethiopica were species-specific, while the L. (L.) tropica probe also hybridized with the L. (L.) aethiopica mini-exon repeat. The mini-exon intron-derived probes for T. cruzi, T. rangeli, and T. brucei were species-specific. This method involving the detection of specific PCR-amplified products produced using a single primer set represents a novel sensitive and specific assay for multiple trypanosomatid species and groups.

Animals↗
PubMed1996

Phylogeny of trypanosomes as inferred from the small and large subunit rRNAs: implications for the evolution of parasitism in the trypanosomatid protozoa.

Sequences of the small rRNA genes and partial sequences of the large rRNA genes were obtained by PCR amplification from a variety of vertebrate trypanosomes. The trypanosome species and hosts included Trypanosoma avium from a bird, T. rotatorium from an amphibian, T. boissoni from an elasmobranch, T. triglae from a marine teleost and T. carassii from a freshwater teleost. Phylogenetic relationships among these species and other representatives of the family Trypanosomatidae were inferred using maximum likelihood, maximum parsimony and evolutionary parsimony. The trypanosomatid tree was rooted using rRNA sequences from two species from the suborder Bodonina. All methods showed that the mammalian parasite, Trypanosoma brucei, constitutes the earliest divergent branch. The remaining trypanosomes formed a monophyletic group. Within this group, the bird trypanosome was grouped with T. cruzi, while the elasmobranch trypanosome and the two fish trypanosome species formed a group with an affinity to T. rotatorium. Our results provide no evidence for co-evolution of trypanosomatids and their hosts, either vertebrate or invertebrate. This suggests that evolution of trypanosomatids was accompanied by secondary acquisitions of hosts and habitats.

Animals↗
PubMed1995

Analysis of kinetoplast DNA of freshwater fish trypanosomes.

The sequences of 10 conservative regions (CR) of minicircles of 6 selected isolates of freshwater fish trypanosomes have typical organization of this region with high degree of sequence conservation. The comparison with CRs of other trypanosomatids showed that freshwater fish trypanosomes represent a compact separate group within the genus Trypanosoma. The alignment of all sequences obtained revealed, however, the existence of 2 types of CRs in sequenced minicircles, with the differences concentrated in a short region. Taxonomic consequences of these results are discussed.

Animals↗
PubMed1994

Disruption of RNA editing in Leishmania tarentolae by the loss of minicircle-encoded guide RNA genes.

RNA editing in kinetoplastids appears to be a labile genetic trait that is affected by prolonged cell culture. The transcripts of the G1-G5 cryptogenes are pan-edited in the recently isolated LEM125 strain of Leishmania tarentolae, but not in the UC strain which has been in culture for 55 years. At least 32 minicircle-encoded guide RNAs (gRNAs) for the editing of G1-G5 transcripts are present in LEM125 and absent in UC. We hypothesize that specific minicircle sequence classes encoding gRNAs for the editing of these transcripts were lost during the long culture history of the UC strain. The protein products, which include components of complex I of the respiratory chain, are probably not required during the culture stage of the Leishmania life cycle.

Amino Acid Sequence↗
PubMed1994

Monophyletic origin of beta-division proteobacterial endosymbionts and their coevolution with insect trypanosomatid protozoa Blastocrithidia culicis and Crithidia spp.

Some trypanosomatid protozoa (order Kinetoplastida) are well known to harbor bacterial endosymbionts. Their phylogenetic positions and evolutionary relationships with the hosts were deduced by comparing the rRNA gene sequences. Earlier, we observed that these symbionts from three Crithidia spp. are identical and are closely related to Bordetella bronchiseptica. We have now sequenced the genes of another endosymbiont and the host protozoan Blastocrithidia culicis. The 16S rRNA genes of the Blastocrithidia and Crithidia symbionts share approximately 97% identity and form a distinct group, branching off the B. bronchiseptica lineage in the beta-division of Proteobacteria. Comparison of their secondary structures in the stem regions suggests compensatory mutations of the symbiont sequences, contributing to their biased base transitions from G to A and C to T. Two putative genes encoding tRNA(Ile) and tRNA(Ala) are highly conserved in the otherwise variable internal transcribed spacer region. Comparisons of the host rRNA gene sequences suggest that the symbiont-containing Crithidia and Blastocrithidia are more akin to each other than to other trypanosomatids. The evidence suggests that Blastocrithidia and Crithidia symbionts descend from a common ancestor, which had presumably entered an ancestral host and thence coevolved with it into different species. We therefore propose naming the symbionts Kinetoplastibacterium blastocrithidii and Kinetoplastibacterium crithidii.

Animals↗
PubMed1994

Evolution of RNA editing in kinetoplastid protozoa.

The editing of RNA in trypanosomatid mitochondria involves the insertion and occasional deletion of uridine residues within coding regions of maxicircle messenger RNA transcripts. The extent to which the transcripts of homologous genes undergo editing differs in different species. In some, entire genes are edited (pan-editing), whereas in others, editing is limited to the 5' termini of editing domains (5' editing). Here we investigate which type of editing is ancestral and which is derived, by analysing RNA editing in the different lineages, using a kinetoplastid phylogeny reconstructed from nuclear small subunit ribosomal RNA sequences. We conclude that the ancestral cryptogenes were pan-edited, and we hypothesize that the 5'-edited homologues were generated by several independent events from partially edited RNAs, in which case editing may be a more primitive mechanism than previously thought.

Adenosine Triphosphatases↗