Analysis of the cDNA and encoded protein of the human testis‐specific PGK2 gene

Abstract

Because of their unique function, germ cells require unique gene products. Thus, although the glycolytic enzyme phosphoglycerate kinase (PGK) is required in all metabolically active cell types, there are two functional PGK genes in the mammalian genome, one, PGK-1, that is X-linked and ubiquitously expressed in all somatic tissues, and a second, PGK-2, that is autosomal and expressed only in spermatogenic cells. Expression of the PGK-2 gene may function solely to compensate for repressed expression of the PGK-1 gene due to X-chromosome inactivation in spermatocytes. Alternative y, the PGK-2 gene could encode an isozyme with unique characteristics that are beneficial to spermatozoa. We have isolated a cDNA of the human PGK-2 gene and used this as probe to demonstrate that transcription of this gene in spermatocytes and spermatids coincides with a period of repressed transcription of the X-linked PGK-1 gene during spermatogenesis in the human testis. We have also analyzed the amino acid sequence and protein characteristics of the PGK-2 isozyme deduced from this cDNA and compared them with that of the human PGK-1 isozyme to show that known structural and functional motifs are conserved in both proteins. Finally, we have examined the distribution of the PGK-1 and PGK-2 isozymes during spermatogenesis in the mouse to show that while the PGK-2 protein does not appear to possess any unique intracellular localization signal, it is more stable in vivo than the PGK-1 protein.

Identification and Analysis of Over 2000 Ribosomal Protein Pseudogenes in the Human Genome

“…They are typically characterized by a complete lack of introns, the presence of small flanking direct repeats, and a polyadenine tract near the 3Ј end (provided that they have not decayed). Processed pseudogenes in general are not transcribed, however in very rare cases, transcripts of some pseudogene have been reported, although the functional relevance of these pseudogene transcripts remains unclear (McCarrey et al 1996;Fujii et al 1999;Olsen and Schechter 1999).It is unclear how many pseudogenes exist in the human genome. Estimates for the number of human genes range from ∼ 22,000 to ∼ 75,000 (Crollius et al 2000;Ewing and Green 2000;Lander et al 2001;Venter et al 2001;Harrison et al 2002b).…”

“…They are typically characterized by a complete lack of introns, the presence of small flanking direct repeats, and a polyadenine tract near the 3Ј end (provided that they have not decayed). Processed pseudogenes in general are not transcribed, however in very rare cases, transcripts of some pseudogene have been reported, although the functional relevance of these pseudogene transcripts remains unclear (McCarrey et al 1996;Fujii et al 1999;Olsen and Schechter 1999).…”

Establishment and applications of male germ cell and Sertoli cell lines

“…In phenotype, synaptonemal complexes are undetected in the nuclei of GC-1spg cells, which usually appear in the leptotene or later spermatocytes (West et al 2010). In addition, GC-1spg cells are positive for lactate dehydrogenase-C4 (LDHC4) isozyme, a marker specific for meiotic and postmeiotic germ cells (Liang et al 1986); however, these cells are negative for phosphoglycerate kinase 2 (PGK2), which is normally expressed in secondary spermatocytes (McCarrey et al 1996). Based on its morphological and biochemical features, GC-1spg cell line corresponds to the characteristics of cells between type B spermatogonia and preleptotene spermatocytes.…”

The abundance of processed pseudogenes derived from glycolytic genes is correlated with their expression level

“…For example, the gene coding for phosphoglycerate kinase (PGK) generated two intronless sequences. The first, JPGK-1, is a processed pseudogene but the second, PGK2, produces a transcript that is expressed in the germ line during spermatogenesis (McCarrey et al 1996).…”