| Accurate transcription in eukaryotic organisms requires RNA polymerase II and several general transcription factors (GTFs; TFIIA, B, D, E, F, H). These factors have previously been believed to be universal for transcription in all cell types. However, it has recently been reported that there are different isoforms of the GTFs that may be involved in transcription regulation only in germ cells. How those new factors are expressed and how they regulate the germ cell development is not well understood. I address these problems in this thesis.;In Chapter 1, I describe studies in which I characterize the expression of the testis-specific transcription factor ALF, an isoform of the large subunit of TFIIA, as well as other transcription factors. I found that the ALF gene starts to be expressed during the pachytene stage of prophase I of spermatogenesis. These studies also show that there is a coordinated induction of many general transcription factors during male germ cell development.;In Chapter 2, I investigate the possibility that ALF is expressed in female germ cells. The data show that ALF is expressed in oocytes in Xenopus, and that it completely replaces its somatic counterpart TFIIA. This substitution is reversed by hormone treatment during oocyte maturation. Furthermore, inactivation of ALF by antibody injection inhibits transcription of reporter genes, suggesting that ALF plays a functional role in transcription in female germ cells. Finally, I show that TFIIA is translationally inactive during oogenesis.;In Chapter 4, I investigate sequences that control ALF gene expression in transgenic mice. I show that an inactive methylated ALF promoter can be reversed by 5-aza, 2'-deoxycytidine treatment. Further, consistent with results in Xenopus, I show that ALF is also expressed in mouse oocytes.;In summary, this work describes distinct expression characteristics for a new germ cell-specific general transcription factor ALF. The data also show that this factor is a functional replacement for its somatic counterpart during oogenesis. The significance of this work is that I extend data on a male-specific factor to female germ cells, and show the physical and functional interchange between transcription factors in germ and somatic tissues. |
