Biomedical subjects

I M Adham

Publications and source records attributed to I M Adham.

44 records · Page 3Linked to original sources

PubMed1990

Nucleotide sequence and exon-intron organization of the human proacrosin gene.

Acrosin is a serine proteinase and located in a zymogen form, proacrosin, in the acrosome of the sperm. As deduced from the cDNA sequences for human and boar proacrosin, the enzyme is synthesized as a preproenzyme, preproacrosin, which contains a hydrophobic leader sequence. Using cDNA clones as probes, we have isolated the gene coding for human proacrosin from a human leucocyte genomic library and a human cosmid library, respectively. The gene contains four introns between 0.2 kb--4.5 kb in length. Similar to other serine proteinases, the coding sequence of the preproacrosin gene is spread over all the five exons of the gene and the three activesite residues His, Asp and Ser are encoded by three different exons. According to the exon-intron structure, preproacrosin is suggested to be closely related to the serine proteinase subfamily containing trypsin and kallikrein. However, the light chain of proacrosin seems to be similar to that of chymotrypsin. The coding of the serine active-site residue together with the proacrosin-specific proline-rich domain in one exon, namely exon E5, let us assume that the nucleotide sequence for the proline-rich domain was generated during evolution by intron-exon transfer from a foreign gene with subsequent intron excision. By primer extension analysis, the transcription initiation site of the preproacrosin mRNA could be assigned to the residue C at -74 nucleotides upstream from the translation initiation codon ATG. In contrast to most other eucaryotic genes, including the known testis-specific genes, typical TATA and CAAT box sequences in convential distances from the 5' end of the transcription start site could not be evaluated in the proacrosin gene.

Acrosin↗

PubMed1990

Molecular cloning of human preproacrosin cDNA.

Complementary DNA-clones for human preproacrosin have been isolated from a human testis cDNA library in lambda gt11. The nucleotide sequence of the 1402 bp cDNA insert includes a 20 bp 5' noncoding region, an open reading frame of 1263 bp corresponding to 421 amino acids (45.9 kdalton), and a 105 bp 3' untranslated region. The deduced amino acid sequence is compared with that recently evaluated from a cDNA clone for boar preproacrosin. The sequence identity is 70%; the leader sequence, the catalytic triad (His, Asp, Ser; which is characteristic for serine proteinases) and the positions of the cysteine residues crosslinking the light and the heavy chain of the active enzyme, acrosin, are conserved in both species. At the C-terminal end, a proline-rich sequence is present in both species; this may represent the species-specificity of acrosin.

Acrosin↗

PubMed1990

Genomic sequences of human protamines whose genes, PRM1 and PRM2, are clustered.

Protamines are small, arginine-rich proteins involved in the condensation of sperm chromatin. Using cDNA clones, we have isolated the genes for both human protamines, i.e., protamine 1 (PRM1) and protamine 2 (PRM2), from a human cosmid library. Each of these genes contains a single intron consisting of 91 and 163 bp, respectively. From the 5'-noncoding region of PRM1 664 bp and from the 5'-noncoding region of PRM2 902 bp were determined. Both genes contain typical TATAA and CAAT boxes at conventional distances from the transcription start points, which by using primer extension experiments could be assigned to nucleotides -91 and -110 for PRM1 and PRM2 genes, respectively. Comparison of the 5'-noncoding regions of PRM1 and PRM2 genes reveals 12 different motifs in common, 8 of which are clustered in both genes and could reflect regulatory elements for testis- and spermatid-specific gene expression. Both human genes have been found to be clustered at a distance of 4.8 kb. Comparison of the genomic organization of human and mouse protamine genes revealed greater similarities between the two in the 5'-noncoding region.

Amino Acid Sequence↗

PubMed1990

Nucleotide sequence of the gene for human transition protein 1 and its chromosomal localization on chromosome 2.

Transition protein 1 (TNP1) is a highly basic nuclear protein of 54 amino acids that is found in haploid spermatogenic cells during the period of transition of histones to protamines. Using the cDNA clone for human TNP1, we have isolated the gene encoding human TNP1 from human genomic libraries. The gene contains an intron of 200 bp; 1104 bp of the 5'- and 276 bp of the 3'-noncoding region have been sequenced. Comparison with the rat TNP1 gene yielded a similarity of 77% over the region between the transcription start point and the polyadenylation signal. The gene contains typical CAAT and TATAA boxes at conventional distances from the transcriptional start site. Using a series of human-rodent somatic cell hybrids containing variant complements of human chromosomes, the TNP1 gene was found to cosegregate with human chromosome 2. By in situ hybridization, the gene was assigned to the q35 and q36 bands of the long arm of chromosome 2. This chromosomal region encodes several genes, including TNP1, that are located on murine chromosome 1.

Amino Acid Sequence↗

PubMed1990

Mouse preproacrosin: cDNA sequence, primary structure and postmeiotic expression in spermatogenesis.

The primary structure of mouse preproacrosin was deduced by nucleotide sequencing of cDNA clones isolated from a mouse testis cDNA library. The largest cDNA, with 1373 bp, consists of a 11-bp 5'untranslated sequence, a 1254-bp open reading frame terminated by a TGA triplet and a 105-bp 3' untranslated end, including one potential polyadenylation signal. The NH2-terminus of the polypeptide contains a hydrophobic 15-amino acid signal peptide. This cleavable signal sequence is followed by 403 amino acids, representing the acrosin light and the heavy chain of 23 and 380 amino acid residues, respectively. The proteolytic active site segments His, Asp and Ser are part of the heavy chain, as well as a proline-rich COOH-terminus, which is not present in any other serine proteinase studied so far. Furthermore the postmeiotic expression of the preproacrosin gene during mouse spermatogenesis was studied.

Acrosin↗

PubMed1989

Molecular cloning of preproacrosin and analysis of its expression pattern in spermatogenesis.

Complementary DNA clones for the boar preproacrosin have been isolated from a randomly primed testis cDNA library in lambda gt10 and from an oligo(dT)-primed testis cDNA in lambda gt11. The nucleotide sequence of the 1418-bp cDNA insert includes a 46-bp 5'-untranslated region, an open reading frame of 1248 bp corresponding to 416 amino acids (45.59 kDa) and a 121-bp 3'-untranslated region. The deduced amino acid sequence includes the active-site residues histidine, asparagine and serine of the catalytic triad of the serine proteinase super-family and is colinear with that determined by amino acid sequencing of the boar acrosin light chain and of a small region of the NH2-terminal sequence of the heavy chain. The preproacrosin cDNA contains at the 3' end a 381-bp sequence which codes for an amino acid sequence not yet found in any other serine proteinase. This amino acid sequence is rich in proline (42 out of 127 amino acids) and is suggested to be involved in the recognition and binding of the spermatozoa to the zona pellucida of the ovum. The mRNA for preproacrosin is synthesized as an approximately 1.6-kb-long molecule only in the postmeiotic stages of boar and bull spermatogenesis.

Acrosin↗

PubMed1989

The gene encoding the human preproacrosin (ACR) maps to the q13-qter region on chromosome 22.

Human proproacrosin is specified by a single gene (ACR). Using a series of human-rodent somatic cell hybrids containing variant complements of human chromosomes, the preproacrosin gene was found to cosegregate with human chromosome 22. Somatic cell hybrids containing translocation chromosomes carrying parts of chromosome 22 were used to locate the preproacrosin gene to the region 22q13-22qter. By probing the DNA of 82 individuals, a restriction fragment length polymorphism was found with SstI in 14 cases.

Acrosin↗

PubMed1989

Nucleotide sequences and expression of cDNA clones for boar and bull transition protein 1 and its evolutionary conservation in mammals.

During spermatogenesis, the nucleoproteins undergo several dramatic changes as the germinal cells differentiate to produce the mature sperm. With nuclear elongation and condensation, the histones are replaced by basic spermatidal transition proteins, which are themselves subsequently replaced by protamines. We have isolated cDNA clones for one of the transition proteins, namely for TP1, of bull and boar. It turned out that TP1 is a small, but very basic protein with 54 amino acids (21% arginine, 19% lysine) and is highly conserved during mammalian evolution at the nucleotide as well as at the amino-acid level. Gene expression is restricted to the mammalian testis, and the message first appears in round spermatids. Thus production of TP1 is an example of haploid gene expression in mammals. The size of the mRNA for TP1 was found to be identical in 11 different mammalian species at around 600 bp. Hybridization experiments were done with cDNAs from boar and bull, respectively. The positive results in all mammalian species give further evidence for the conservation of the TP1 gene during mammalian evolution and its functional importance in spermatid differentiation.

Amino Acid Sequence↗