SURF5 - A GENE IN THE TIGHTLY CLUSTERED MOUSE SURFEIT LOCUS IS HIGHLYCONSERVED AND TRANSCRIBED DIVERGENTLY FROM THE RPL7A (SURF3) GENE

The four previously characterized genes (Surf1 to 4) of the mouse Surf eit locus do not share any sequence homology, and the transcription of each gene alternates with respect to its neighbor(s). Adjacent Surfei t genes are separated by very small distances, and two of the genes ov erlap at their 3' ends. In this work we have further defined the Surfe it gene cluster by the isolation of Surf5, a fifth gene of the locus, and determination of its relationship to the other Surfeit genes. Surf 5 does not share any sequence homology with the four cloned Surfeit ge nes. The transcription of Surf5 is divergent with respect to its neigh bor the Surf3 gene, and the 5' ends of Surf5 and Surf3 are separated b y only 159 bp, suggesting the presence of a second bidirectional promo ter in the locus. The 3' end of Surf5 maps only 68 bp away from the pr ocessed 3' end of a pseudogene. The human and partial chicken Surf5 co ding regions show greater than 95% identity, and a Caenorhabditis eleg ans homologue shows 38% identity and 56% similarity with the mouse Sur f5 amino acid sequence. The 3.5-kb transcript of Surf5 encodes a small hydrophilic protein of 140 amino acid residues, which differs from th e ribosomal protein L7a encoded by the Surf3 gene or the integral memb rane protein encoded by the Surf4 gene. Subcellular fractionation loca ted the Surf5 protein to the soluble fractionation of the cytoplasm. T he Surfeit locus appears to represent a novel type of gene cluster in which the genes are unrelated by sequence or function; however, their organization may play a role in their gene expression. (C) 1995 Academ ic Press, Inc.