Identification of a gene encoding the predicted ribosomal protein l7b divergently transcribed from POL1 in fission yeast Schizosaccharomyces pombe

Abstract

A 0.85 Kb RNA molecule is transcribed in the region upstream from the 5'-end of the S. pombe POL1 gene encoding the catalytic subunit of DNA polymerase alpha. The nucleotide sequence of the DNA region hybridizing with the 0.85 Kb transcript allowed us to Identify an open reading frame coding for a predicted peptide which shows 50% identity with the rat ribosomal protein L7 and which is transcribed divergently from POLl. We have named this gene RPL7b because of the existence in S. pombe of a different sequence, named RPL7, which aiso codes for a putative protein showing homology with the rat ribosomal protein L7. The RPL7b gene includes a 291 bp-long intron containing the sequences necessary for intron excision and RNA spllcing in S. pombe. The precise location of the intron was estabiished by ampilficatlon and sequencing of a partiai cDNA copy of the mRNA, whereas the Initiation site of transcription was determined by reverse transcription of the 5' region of the mRNA. The 320 bp separating the starting methionine codons of RPL7b and POL1 genes shouid contain the signals necessary for their divergent transcription and regulation. The sequence 5'-AAGACAGTCACA-3', whose primary structure is homologous to a conserved block present in the 5'-untranscribed regions of other S. pombe genes of rlbosomai proteins, is iocated about 50 bp upstream the transcription initiation site of RPL7b. © 1991 Oxford University Press.