| The gene locus encoding the human testis-specific l-lactate dehydrogenase Ldh-c (LDHX, L-lactate:NAD + oxidoreductase, E.C. 1.1.1.27), has been isolated in three genomic clones. Ldh-c contains seven exons and eight intervening sequences, one of which is located in the 5;The cDNA clone 2 leader was 171 nucleotides long as mapped by using mRNA as a template for reverse transcriptase in primer extension analysis. The putative promoter region for this species of RNA was unusual in that there was no TATA or CAAT homologous sequence, however, this area was GC rich with two potential Sp1 binding elements (CCGCCC) upstream of the cap site. The start site for the clone 1 transcript was not mapped, however, two regions homologous to the TATA box consensus sequence and one homologous to the CAAT consensus sequence have been located. Analysis of the sequence of the 124 nucleotides upstream of the start of transcription indicated no homology to known regulatory consensus sequences. However, a CAG triplet was repeated five times and this element has also been found in the upstream regions of testis-specific cytochrome c (Scarpulla, 1981) and testis-specific phosphogylcerate kinase-2 (McCarrey, 1987). The function, if any, is unknown, but this triplet may be involved in testis-specific gene expression. |
