Genes Encoding Drosophila melanogaster RNA Polymerase II General Transcription Factors: Diversity in Tfiia and Tfiid Components Contributes to Gene-Specific Transcriptional Regulation

How have the factors required for transcription initiation (TFIIA, TFIIB, TFIID, TFIIE, TFIIF, TFIIH, and RNA polymerase II [pol II]) evolved to accommodate the elaborate transcriptional programs required for growth, differentiation, and development of multicellular organisms? Here we present analysis of the recently completed Drosophila melanogaster genome sequence, as well as those of Caenorhabditis elegans, Saccharomyces cerevisiae, and humans, that sheds light on this well studied question in eukaryotic biology. All four organisms encode single isoforms of RNA pol II, TFIIB, TFIIE, TFIIF, and TFIIH components, but multiple, sequence-related isoforms of TFIID components (Fig. 1; Albright and Tjian 2000). In addition, Drosophila and humans encode multiple isoforms of TFIIA components (Upadhyaya et al. 1999; Ozer et al. 2000). Current evidence indicates that tissue- and cell type–specific transcription is directed by differentially...