TAK1 - MOLECULAR-CLONING AND CHARACTERIZATION OF A NEW MEMBER OF THE NUCLEAR RECEPTOR SUPERFAMILY

Using polymerase chain reaction and two degenerate primers whose desig ns were based on the two best conserved regions of the DNA-binding dom ain of the nuclear receptor superfamily, we identified and cloned a no vel orphan receptor, named TAK1, The open reading frame of TAK1 encode s a protein of 596 amino acid residues, Based on the modular structure and the presence of a DNA-binding domain containing two zinc fingers TAK1 belongs to the steroid/thyroid hormone receptor superfamily, The amino acid sequence of TAK1 is most closely related to the orphan rece ptor TR2-11, Their overall sequence homology is 64%, with the highest similarity (82%) being observed in the DNA-binding domain, Northern bl ot analysis using RNA from multiple human tissues showed that a 9.4 ki lobase TAK1 transcript was expressed ubiquitously and that the presenc e of a 2.8 kilobase mRNA was largely restricted to the testis, In situ hybridization using sections of rat and mouse testes and Northern blo t analysis using RNA from testes of rats at various ages revealed that TAK1 is most abundantly expressed in spermatocytes whereas little exp ression was observed in other germ cells or somatic cells. In situ hyb ridization using other mouse and rat tissues revealed cell type-specif ic expression of TAK1 in several tissues. Our observations suggest a r ole for this putative transcription factor in the regulation of gene e xpression in specific cell types, In the testis, TAK1 appears to contr ol gene expression during spermatogenesis, particularly during the mei otic phase.