Biomedical subjects

W Albig

Publications and source records attributed to W Albig.

33 records · Page 2Linked to original sources

PubMed1997

Characterization of the H1.5 gene completes the set of human H1 subtype genes.

The H1 histone family in mammals contains at least seven subtypes. In the past we have isolated six of the seven genes encoding these isoforms. To complete the set of the human H1 histone genes, we have designed two PCR primers deduced from a partially published sequence of the remaining histone H1 gene [Carozzi et al. (1984) Science 224, 1115-1118] and from a consensus sequence which we have derived from the conserved region of human histone H1 genes. Using these primers we have amplified a 417-bp DNA fragment from total human DNA. This fragment was used for screening a human phage genomic library. Two overlapping clones were isolated. The region contains a set of 5 genes representing each of the five histone classes. In continuation of our numbering of human H1 genes, we have named this H1 gene H1.5. This gene encodes a protein almost identical to the previously published protein sequence designated H1a [Ohe et al. (1986) J. Biochem. 100, 359-368]; since the changes are in a region of some uncertainty of the peptide sequencing, we conclude that the newly isolated gene codes for the H1a protein. The structures of the flanking regions of the genes except the H2B gene are typical for histone genes. They include: (1) a CCAAT element in the promotor region, (2) a TATA box and (3) a palindromic termination element. The H2B sequence shows no typical regulatory elements and no complete ORF, therefore we consider it as a pseudogene. The expression of the H1.5 gene was examined in several cell lines.

Amino Acid Sequence↗

PubMed1997

Histones: genetic diversity and tissue-specific gene expression.

Histones are the major protein constituents of the chromatin of eukaryotic cell nuclei. This group of basic proteins is extremely conserved throughout evolution and includes five classes termed H1, H2A, H2B, H3 and H4. In mammals, each of these classes except H4 is subdivided into several subtypes. The most divergent class of histones is the H1 protein family, which consists of seven different subtypes, termed H1.1-H1.5, H1 degree, and H1t. The subtypes H1.2 and H1.4 are found in most somatic cell nuclei, whereas H1 degree is found in several differentiated tissues, and H1t is restricted to mammalian testicular cells. Similarly, core histone subtypes replacing the major forms of H2A, H2B or H3 have been described. Biochemical analysis of protein and RNA from different tissues and cell lines demonstrates varied patterns of expression of individual histone subtype genes. Moreover, antibodies against specific histone subtypes and in situ hybridization with subtype-specific probes indicate that the expression of histone subtype genes is in several cases modulated in a tissue-specific manner. This is particularly evident at the different stages of spermatogenesis when chromatin undergoes substantial reorganization, which finally results in the highly condensed state of chromatin of the mature sperm head.

Animals↗

PubMed1997

The human histone gene cluster at the D6S105 locus.

The sequences and organization of the histone genes in the histone gene cluster at the chromosomal marker D6S105 have been determined by analyzing the Centre d'Etude du Polymorphisme Humain yeast artificial chromosome (YAC) 964f1. The insert of the YAC was subcloned in cosmids. In the established contig of the histone-gene-containing cosmids, 16 histone genes and 2 pseudogenes were identified: one H1 gene (H1.5), five H2A genes, four H2B genes and one pseudogene of H2B, three H3 genes, and three H4 genes plus one H4 pseudogene. The cluster extends about 80 kb with a nonordered arrangement of the histone genes. The dinucleotide repeat polymorphic marker D6S105 was localized at the telomeric end of this histone gene cluster. Almost all human histone genes isolated until now have been localized within this histone gene cluster and within the previously described region of histone genes, about 2 Mb telomeric of the newly described cluster or in a small group of histone genes on chromosome 1. We therefore conclude that the data presented here complete the set of human histone genes. This now allows the general organization of the human histone gene complement to be outlined on the basis of a compilation of all known histone gene clusters and solitary histone genes.

Chromosome Mapping↗

PubMed1997

Varied expression patterns of human H1 histone genes in different cell lines.

Five main type H1 histones have been described in man (H1.1-H1.5) in addition to the testis specific type H1t and the replacement subtype H1 degrees, which is found mainly in highly differentiated cells. We have isolated this whole complement of H1 genes and have studied the expression of the seven human H1 subtype genes in several cell lines. The RNAase protection assay was used to discriminate between the very similar transcripts derived from the seven H1 subtype genes. With the exception of H1.2 and H1.4, we found substantial differences between the H1 mRNA levels in the different cell lines tested. No H1.1 mRNA was detected in most of the cell lines and just a low level of H1.1 mRNA was found in human testis. In contrast to the differential patterns of the other subtypes, H1.2 and H1.4 were in all cells expressed at a high level, indicating a basal function compared with the other H1 histones. Because differences in the timing of H1 protein subtype synthesis have been reported, we have analyzed the kinetics of accumulation of H1 subtypes in synchronized HeLa cells and observed that all H1 subtypes examined (H1 degrees, H1.2-H1.5) were expressed in a replication-dependent manner. The analysis showed a differential rise of mRNA levels during S-phase, from four-fold (H1 degrees) to 15-fold (H1.5). Our results may point at a specific function of each subtype and suggest that expression of the H1 histone subtype genes depends on common S-phase-depent factors as well as on individual regulatory systems. Thus, the data presented here provide a basis for further analysis of the regulation and function of the complex H1 gene and protein family.

Cell Line↗

PubMed1997

Physical mapping of two histone gene clusters on human chromosome 6p22.1-22.2.

Histones are basic proteins which are responsible for the assembly and maintenance of the nucleosomal structure within the chromosomal fiber in eukaryotes. Two clusters of these genes have previously been mapped to the region 6p21.1-p22.2. We describe here a radiation hybrid map, a long range restriction map and a YAC contig covering and linking these two clusters and giving the precise localisation with respect to the HLA complex. The large cluster contains five H1 histone genes in the 6p22.2 region, the smaller only one, H1F5 (H1.5), in 6p22.1. In both clusters, each H1 locus is accompanied by several core histone genes. The large cluster has additionally been covered by a sequence ready PAC contig and three probably unrelated genes (TRMI2, BTN and SSADH) have been accurately localized within the 6p22.2-p22.1 region.

Chromosomes, Human, Pair 6↗

PubMed1996

Testis-specific expression of a novel human H3 histone gene.

We have investigated the expression of a recently described, solitary human H3 histone gene. Using RNase protection assays, the corresponding mRNA could only be detected in RNA preparations from human testis, whereas several human cell lines and somatic tissues did not exhibit expression of this gene. In situ hybridization of sections from human testis revealed expression to be confined to primary spermatocytes. In addition to H1t, this novel H3 gene, which is located on chromosome 1, is the second tissue-specific human histone gene that has been found to be expressed solely in the testis.

Adult↗

PubMed1996

A solitary human H3 histone gene on chromosome 1.

A solitary histone H3 gene encoding a novel H3 protein sequence has been isolated. This H3 gene maps to chromosome 1 (1q42), whereas we have shown previously that the majority of the human histone genes form a large cluster on chromosome 6 (6p21.3). In addition, a small cluster has been described at 1q21. The clustered histone genes are expressed during the S-phase of the cell cycle, hence their definition as replication-dependent histone genes. In contrast, expression of replacement histone genes is essentially cell-cycle independent; they are solitary genes and map outside the major clusters. The newly described H3 gene maps outside all known histone gene clusters and varies by four amino acid residues from the consensus mammalian H3 structure. In contrast to other solitary histone genes, this human H3 gene shows the consensus promoter and 3' flanking portions that are typical for replication-dependent genes.

Base Sequence↗

PubMed1996

Chromosome mapping of rat histone genes H1fv, H1d, H1t, Th2a and Th2b.

Chromosome assignment of the rat histone genes H1t, H1d (H1.4), H1fv (H10), Th2a and Th2b is described. The testicularly expressed histone genes H1t, Th2a and Th2b could be assigned to rat chromosome (RNO) 17 by PCR analysis of somatic cell hybrid DNAs. The H1d gene was mapped to RNO17p12-->p11 by FISH. These genes might form a histone gene cluster homologous to that found on HSA6p21.3 in humans and MMU13A2-3 in mice. The rat histone H1fv gene was assigned to RNO7 by PCR. This result allows the inclusion of rat H1fv to an established conserved group of syntenic genes in rat, mouse and human on chromosomes RNO7, MMU15 and HSA22, respectively.

Animals↗

PubMed1995

The human replacement histone H3.3B gene (H3F3B).

H3.3 is a replacement histone subtype that is encoded by two replication-independent genes termed H3.3A and H3.3B, respectively. We have isolated a fullsize H3.3 cDNA clone from an oligo(dT)-primed human testicular cDNA library. Subsequently, the corresponding gene was isolated from a human cosmid library and was identified as the H3.3B gene. It was the only histone gene on this 42-kb cosmid clone. The gene structure shows characteristic features of an H3.3 gene. First, it contains an intron of about 0.5 kb in the 5' untranslated region and two smaller introns within the coding gene portion. Second, no histone gene-specific dyad symmetry element was found in the 3' untranslated region, but three putative polyadenylation signals were detected downstream of the gene. The corresponding transcripts were detected by Northern blot analysis using poly(A)+ RNA from testis and from the HEK293 tumor cell line. The newly discovered human H3.3B gene (HGMW-approved symbol H3F3B) was mapped by fluorescence in situ hybridization to the telomeric region of chromosome 17 (17q25). This localization of the H3.3B gene and its solitary arrangement contrast with the majority of the replication-dependent histone genes, which form a large cluster on chromosome 6 and a second cluster on chromosome 1.

Amino Acid Sequence↗

PubMed1994

Organization and expression of H1 histone and H1 replacement histone genes.

The H1 family is the most divergent subgroup of the highly conserved class of histone proteins [Cole: Int J Pept Protein Res 30:433-449, 1987]. In several vertebrate species, the H1 complement comprises five or more subtypes, and tissue specific patterns of H1 histones have been described. The diversity of the H1 histone family raises questions about the functions of different H1 subtypes and about the differential control of expression of their genes. The expression of main type H1 genes is coordinated with DNA replication, whereas the regulation of synthesis of replacement H1 subtypes, such as H1 zero and H5, and the testis specific H1t appears to be more complex. The differential control of H1 gene expression is reflected in the chromosomal organization of the genes and in different promoter structures. This review concentrates on a comparison of the chromosomal organization of main type and replacement H1 histone genes and on the differential regulation of their expression. General structural and functional data, which apply to both H1 and core histone genes and which are covered by recent reviews, will not be discussed in detail.

Amino Acid Sequence↗

PubMed1993

Association of a human H1 histone gene with an H2A pseudogene and genes encoding H2B.1 and H3.1 histones.

A cluster of human histone genes was found on three overlapping clones isolated from cosmid and bacteriophage libraries. These three overlapping segments of the human genome comprise genes coding for H3.1, an H2A pseudogene, and an H2B.1 gene downstream of the previously characterized H1.2 gene. The cosmid clone covers 30 kb upstream of the H1.2 gene and overlaps with two phage clones covering the core histone genes and the pseudogene. The same arrangement of an H3 gene, an H2A pseudogene and an H2B gene downstream of an H1 gene has been described within a mouse histone gene cluster [Yang et al.:J Biol Chem 262:17118-17125, 1987; Gruber et al.:Gene 95:303-304, 1990].

Amino Acid Sequence↗

PubMed1993

All known human H1 histone genes except the H1(0) gene are clustered on chromosome 6.

PCR analysis of chromosomal DNA from a panel of human-rodent somatic cell hybrids revealed that the five human H1 histone genes H1.1 to H1.5 and the gene encoding the testis-specific H1t subtype, all of which form clusters with core histone genes, are located on chromosome 6. The H1(0) subtype, which is not neighbored by core histone genes, maps to chromosome 22. Fluorescence in situ hybridization with human metaphase chromosomes and PCR analysis of somatic cell hybrid DNA carrying only fragments of chromosome 6 revealed the region 6p21.1 to 6p22.2 as the histone gene cluster region.

Animals↗

PubMed1991

Glucose repression in Saccharomyces cerevisiae is directly associated with hexose phosphorylation by hexokinases PI and PII.

Genetic and biochemical analyses showed that hexokinase PII is mainly responsible for glucose repression in Saccharomyces cerevisiae, indicating a regulatory domain mediating glucose repression. Hexokinase PI/PII hybrids were constructed to identify the supposed regulatory domain and the repression behavior was observed in the respective transformants. The hybrid constructs allowed the identification of a domain (amino acid residues 102-246) associated with the fructose/glucose phosphorylation ratio. This ratio is characteristic of each isoenzyme, therefore this domain probably corresponds to the catalytic domain of hexokinases PI and PII. Glucose repression was associated with the C-terminal part of hexokinase PII, but only these constructs had high catalytic activity whereas opposite constructs were less active. Reduction of hexokinase PII activity by promoter deletion was inversely followed by a decrease in the glucose repression of invertase and maltase. These results did not support the hypothesis that a specific regulatory domain of hexokinase PII exists which is independent of the hexokinase PII catalytic domain. Gene disruptions of hexokinases further decreased repression when hexokinase PI was removed in addition to hexokinase PII. This proved that hexokinase PI also has some function in glucose repression. Stable hexokinase PI overproducers were nearly as effective for glucose repression as hexokinase PII. This showed that hexokinase PI is also capable of mediating glucose repression. All these results demonstrated that catalytically active hexokinases are indispensable for glucose repression. To rule out any further glycolytic reactions necessary for glucose repression, phosphoglucoisomerase activity was gradually reduced. Cells with residual phosphoglucoisomerase activities of less than 10% showed reduced growth on glucose. Even 1% residual activity was sufficient for normal glucose repression, which proved that additional glycolytic reactions are not necessary for glucose repression. To verify the role of hexokinases in glucose repression, the third glucose-phosphorylating enzyme, glucokinase, was stably overexpressed in a hexokinase PI/PII double-null mutant. No strong effect on glucose repression was observed, even in strains with 2.6 U/mg glucose-phosphorylating activity, which is threefold increased compared to wild-type cells. This result indicated that glucose repression is only associated with the activity of hexokinases PI and PII and not with that of glucokinase.

Enzyme Repression↗

PubMed1991

Isolation and characterization of two human H1 histone genes within clusters of core histone genes.

Two human H1 histone genes, termed H1.3 and H1.4, were isolated from two cosmid clones. The H1.4 gene is associated with an H2B gene, whereas genes coding for all four core histones are located in the vicinity of the H1.3 gene. This cluster arrangement was found both in the two cosmid clones and on overlapping bacteriophage clones isolated from an EMBL3 library. In continuation of our previous analysis of two human H1 genes, this analysis raises the number of completely sequenced H1 histone genes within clusters of core histone genes to four.

Amino Acid Sequence↗

PubMed1988

Structure of yeast glucokinase, a strongly diverged specific aldo-hexose-phosphorylating isoenzyme.

Saccharomyces cerevisiae glucokinase (GLK) is the only described hexose-phosphorylating enzyme specific for aldo-hexoses. The gene was cloned by complementation of a triple mutant lacking all hexose-phosphorylating isoenzymes. Restriction sites were confirmed by genomic hybridization and GLK1 was mapped on chromosome III by ROFAGE, a method derived from the orthogonal field alteration gel electrophoresis. The mapping data were in agreement with previous genetic data. The open reading frame was established by two transcription start points in front of the initial ATG codon and by C-terminal beta-galactosidase fusions. The mRNA is 1.75 kb long and codes for 500 amino acid (aa) residues. Diversity of GLK from hexokinases PI and PII is very marked, with only 26 and 28% overall aa homology. A central core of about 350 aa shows 39% homology. No cross-hybridization could be observed by Southern hybridization. However, strong homologies were found over a range of 11 aa between glucokinase, yeast hexokinases (PI, PII) and rat hexokinase with 8 aa in common. These strongly conserved homologies give support to the view that this aa region corresponds to the binding site for glucose. Unlike all other hexose-phosphorylating enzymes, there is no proline residue indicating a conformational turn next to this glucokinase region. This finding may explain the failure of fructose phosphorylation. In both GLK and the hexokinases, a lysine residue is also conserved at aa position 110 which probably corresponds to the ATP-binding site. Additionally, a consensus sequence of 8 aa residues which is common for ATP-binding enzymes is conserved within the C-terminal part of GLK. The codon bias index for GLK1 is 0.25, which is very low compared with other glycolytic enzymes described so far. The gene is moderately expressed and constitutive on different carbon sources investigated. GLK1 null alleles had no detectable effects on sporulation and growth. Hence, a physiological role for GLK, which might explain its preservation, could not be detected under our laboratory test conditions.

Amino Acid Sequence↗