Boar transition protein 2 and 4 isolated from late spermatid nuclei by high-performance liquid chromatography

The nucleotide sequence of boar transition protein 2 (TNP2) cDNA and haploid expression of the gene during spermatogenesis

A cDNA clone coding for boar transition protein 2 (TNP 2) was isolated from a randomly primed cDNA library of boar testis. Sequence analysis revealed an open reading frame of 414 bp (corresponding to 138 amino acids), 33 bp of the 5' untranslated and about 300 bp of the 3' untranslated region. As compared to TNP 2 of mouse and rat, similarity with TNP 2 of the boar is approximately 70% at the nucleotide level and only about 40% on the basis of amino acid sequence. The similarity between boar and bull TNP2 is 77% and 64%, respectively. Northern blot experiments with RNA of different boar tissues and in situ hybridization on mature boar testis sections revealed testis-specific expression of the TNP 2 gene which is restricted to haploid germ cells. Hybridization experiments of boar TNP2 cDNA with testicular RNA of boar, bull, rat and mouse revealed decreasing intensities of the hybridization signals. With human testicular RNA no hybridization could be obtained.

Sequence analysis of the conserved protamine gene cluster shows that it contains a fourth expressed gene

Structural data are presented on the protamine gene cluster (PGC) of human, mouse, rat, and bull. By restriction mapping we demonstrate that the organization of the protamine cluster is conserved throughout all four species, i.e., the genes are situated in a head to tail arrangement in the order: protamine 1-protamine 2-transition protein 2. Further, we established the nucleotide sequence of the entire human PGC (25 kb in total) and the 3' portion of the rat protamine cluster (PRM2 and TNP2 genes and intergenic region). In addition, a 1 kb fragment of the bovine and murine protamine cluster, situated between PRM2 and TNP2, was sequenced. This fragment is conserved regarding sequence, position, and orientation in all species examined, and was classified as likely coding region by gene recognition program GRAIL. Using the rat fragment as a probe in RNA blots, we detected a testis-specific signal of about 0.5 kb. Finally, we demonstrate a high density of Alu elements, both full and fragmented copies, in the human PGC and discuss their localization with respect to evolutionary and functional aspects.

The amino acid sequence and interaction with the nucleosome core DNA of transition protein 4 from boar late spermatid nuclei

The primary structure of transition protein 4 (TP4) from boar late spermatid nuclei was determined by automated Edman degradation of S-pyridylethylated protein and of peptides generated by cleavage with Staphylococcus aureus V8 protease, lysyl endopeptidase and CNBr. Boar TP4 is a basic protein consisting of a highly basic amino-terminal half (residues 1-73) and a less basic carboxy-terminal half (residues 74-138). The latter half includes a highly hydrophobic segment, a four-times tandemly repeated sequence, N(G)QNKR(K)X, and a carboxy-terminal segment containing Trp126. Ultraviolet absorption and CD spectra of TP4-rat-liver-nucleosome-core-DNA (double-stranded DNA) complexes suggest a TP4-induced local melting of DNA. Although at 1 mM NaCl TP4 brought about a slight stabilization of the DNA against thermal melting, a destabilization of the DNA was observed at 50 mM NaCl. From the results of quenching of tryptophan (Trp126) fluorescence of TP4 upon its binding to double-stranded and single-stranded boar liver nucleosome-core DNA at 50 mM NaCl, the apparent association constants for the binding of TP4 to double-stranded and single-stranded DNA were calculated to be 7.3 x 10(3) M-1 and 4.1 x 10(3) M-1, respectively. These results suggest that TP4, having different domain structures from TP1-3 and a higher affinity for double-stranded DNA, induces a local destabilization of DNA probably through the stacking of Trp126 with nucleic acid bases.

Coordinate expression of the PRM1, PRM2, and TNP2 multigene locus in human testis

Maintenance of the transcriptionally inert state of the mature human spermatozoon requires the expression of the various members of the human protamine gene cluster prior to the final stages of spermatogenesis. During this process, known as spermiogenesis, round spermatids morphologically differentiate into mature spermatozoa. The expression of the PRM1, PRM2, and TNP2 genes facilitates the compaction and condensation of the genetic material within the developing spermatid. To understand better the coordinate control governing this transformation, we have examined the localization and distribution of the human protamines PRM1 and PRM2 and transition protein TNP2 transcripts during human spermatogenesis. The stage-specific expression of these transcripts was determined by in situ hybridization analysis using [alpha-35S]-labeled cRNA probes. PRM1, PRM2, and TNP2 transcripts were abundant in association with round and elongating spermatids, located in the adluminal region of the seminiferous epithelium. They were not observed in association with spermatogonia, spermatocytes, Sertoli cells, or interstitial cells. These data indicate that the human PRM1, PRM2, and TNP2 transcripts are expressed postmeiotically in round and elongating spermatids. The quantitative evaluation of each transcript was determined as a function of the relative optical density per unit area. In all cases examined, the relative level of each transcript was consistent with the following pattern, PRM2 > PRM1 congruent to TNP2.

The gene for human transition protein 2: nucleotide sequence, assignment to the protamine gene cluster, and evidence for its low expression

We have isolated the gene for transition protein 2 (TNP2) from a human cosmid clone that contains the genes for protamines 1 and 2. A nucleotide sequence of 1776 bp that comprises 268 bp of the 5'-noncoding region, 400 bp of exon 1, 849 bp of an intron, 17 bp of exon 2, and 242 bp of the 3'-noncoding region was determined. A modified CAT box, a TATAA box, and two possible polyadenylation sites were identified. Transcripts in testicular RNA could be detected only by RT-PCR and RNase protection assays. By direct sequencing of the PCR products, a cDNA sequence was established. It can be deduced from these results that, in contrast to other mammalian genes, the human TNP2 gene is expressed at a very low level. The human gene differs from that of other mammalian species by the absence of a conserved GCCATCAC nucleotide sequence in the 3'-untranslated region. Since both protamine genes are known to be localized on chromosome 16p13.3, this chromosomal localization holds true for the human TNP2 gene as well. The genes for both protamines and TNP2 are arranged in a DNA stretch of 13 kb.

Characterization of four genes encoding basic proteins of the porcine spermatid nucleus and close linkage of three of them

Protamines and transition proteins (TNP) play a major role during spermatogenesis and spermatid differentiation. By screening a porcine genomic library with the corresponding cDNAs, we isolated the genomic clones for porcine protamines 1 and 2 as well as for transition proteins 1 and 2. Analysis and comparison of exon-intron structure, 5' and 3' untranslated regions and transcription start points revealed features common to their counterparts in other mammals. In contrast to TNP2 the gene for TNP1 is well conserved among species, indicating a non species-specific function in the chromatin condensation of the spermatid nucleus. Furthermore, Southern blot hybridization of digested phage DNA demonstrated close linkage between both protamine genes and the gene for transition protein 2 in a 13-kb stretch of DNA. Our observations support the hypothesis that these genes may have evolved by gene duplication.

Characterization of a gene encoding a basic protein of the spermatid nucleus, TNP2, and its close linkage to the protamine genes in the bull

During elongation and condensation of the spermatid nucleus, histones are replaced by spermatid-specific transition proteins (TNP). TNP1 is well characterized at the cDNA and at the genomic level and was found to be highly conserved during mammalian evolution (similarity between 83 to 98%). We here describe for the first time the nucleotide sequence and organization of the gene for TNP2. The gene was isolated from a bull cosmid library and was found to contain a single intron of 910 bp. The coding sequence consists of 390 bp and has a similarity of about 70% to that of the TNP2 cDNAs of mouse and rat. At the basis of amino-acid sequences, the bull TNP2 is 14 and 15 amino acids longer than that of mouse and rat, respectively, and the similarity is only 45% between bull and mouse and 42% between bull and rat. However, the evolutionary divergence has not occurred at the cost of basic amino acids which are of functional importance in DNA-protein interaction in the condensing spermatid nucleus. The TNP2 gene is closely linked to the protamine genes in the bull genome.