MOLECULAR-CLONING OF DROSOPHILA TFIID SUBUNITS

TRANSCRIPTION initiation factor TFIID is a multisubunit complex contai ning a TATA-box-binding factor (TFIIDtau/TBP) and associated polypepti de factors (TAFs) with sizes ranging from M(r) approximately 20,000 to >200,000 (refs 1-7). As a result of direct promoter interactions8,9, TFIID nucleates the assembly of RNA polymerase II and other initiation factors into a functional preinitiation complex10. Although the nativ e TFIID complex mediates both basal and activator-dependent transcript ion in reconstituted systems, TBP itself is competent for only basal t ranscription. Thus, TAFs are essential cofactors for regulated transcr iption. The complementary DNAs encoding the p230 (M(r) 230,000), p110 and p85 subunits of TFIID have recently been cloned11-18. Here we repo rt the molecular cloning and characterization of the p62, p42, p28 and p22 subunits. These participate in a network of heterogeneous protein -protein interactions within TFIID. Sequence similarities between p62/ p42 and the histones H4/H3, respectively, suggest that these subunits have a functional relationship with chromatin.