A specific programme of gene transcription in male germ cells.

The differentiation of male germ cell requires spermatogenic stage and cell-specific gene expression that is achieved by unique chromatin remodelling, transcriptional control, and the expression of testis-specific genes or isoforms. Specialized transcription complexes that coordinate the differentiation programme of spermatogenesis have been found in germ cells, which display specific differences in the components of the general transcription machinery. The TATA-binding (TBP) protein family and its associated co-factors, for example, show upregulated expression in testis. In this physiological context, transcriptional control mediated by the activator CREM represents an established paradigm. In somatic cells, activation by CREM requires its phosphorylation at a unique regulatory site (Ser117) and subsequent interaction with the ubiquitous coactivator CBP. In testis, CREM transcriptional activity is controlled through interaction with a tissue-specific partner, ACT, which confers a powerful, phosphorylation-independent activation capacity. The function of ACT is regulated by a testis-specific kinesin, KIF17b. This study discusses some aspects of the testis-specific transcription machinery, the function of which is essential for the process of spermatogenesis.