Analysis of TFIIH subunit through isolation of the gene from Schizosaccharomyces pombe corresponding to that of Saccharomyces cerevisiae SSL1, reveals the presence of conserved structural motifs

We isolated a Schizosaccharomyces pombe (Sz, pombe) gene encoding the count erpart of the TFIIH subunit Homo sapiens (H. sapiens) p44 and Saccharomyces cerevisiae (S. cerevisiae) SSL1, and we named this gene product p47. Contr ary to the case of SSL1, which is an essential gene of S. cerevisiae, p47 i s not essential for the viability of St. pombe. The deduced amino acid sequ ence revealed that this TFIIH subunit is highly conserved during evolution. Comparison of the primary structures revealed differences in the predicted positions of introns in the Caenorhabditis elegans (C. elegans) gene encod ing the p47 counterpart found during the genome project. A charged cluster in the N-terminal region is present in the two yeasts. Two putative zinc-bi nding motifs, an extended C2H2 zinc finger with a 'C8 motif and a second pu tative zinc-binding motif common to the two TFIIH subunits, were also found , the former being completely conserved. The latter motif consists of five cysteine residues and is also present in hp44, SSL1 and another TFIIH subun it, human p34 (hp34). Since one zinc atom can bind to four ligands in zinc- binding motifs, the conservation of cysteine residues was given attention. This motif is completely conserved in p47 homologues derived from the four species. As one cysteine residue is not conserved among the homologues of h p34, the consensus of this motif is concluded to be Cys-X2-Cys-X(10,12)-Cys -X2-Cys. This nucleotide sequence has been deposited in the GenBank Data Li brary under Accession Number AF017646. Copyright (C) 1999 John Wiley & Sons , Ltd.