252. Regulated nuclear import of TATA binding protein associated factor 9 (TAF9) in spermatogenesis

Abstract

Spermatogenesis, the differentiation process resulting in the production of haploid germ cells able to fertilise an oocyte, is driven by nuclear transcription factors, and changes in nuclear morphology and function itself. Signal-dependent transport into and out of the nucleus is mediated by members of the importin (IMP) superfamily of transporters, which we have previously shown to change dynamically in expression profile during spermatogenesis. One IMP family member, IMPα2, is expressed during mid to late phase spermatogenesis, implying that it may transport specific cargoes important for these stages, with a potential cargo of significance identified in a yeast 2-hybrid screen being TAF9 (TATA-Binding Protein Associated Factor 9). TAF9 is an integral part of transcription initiation for many genes, such as those with a Downstream Promoter Element in the core promoter and those with activators such as SOX18, p53, HSF1, NF-IL6 or NF-κB. In addition it participates in histone acetylation complexes which have been previously described to be important for the completion of spermatogenesis. Our preliminary data confirm the interaction of IMPα2 and TAF9 using a cotransfection approach. We have also shown that the expression of these proteins in the testis is correlated using both publically available Affymetrix data, and immunohistochemistry staining. TAF9, like IMPα2, is expressed in the nucleus of elongating spermatids of the adult rodent testis. Our data are thus consistent with the idea that specific nuclear import of TAF9 by IMPα2 may be a critical step in the later stages of spermatogenesis.