Identification and characterization of a serine hydroxymethyltransferase isoform in Caenorhabditis briggsae

In the nematode Caenorhabditis elegans, the maternal effect lethal gene mel -32 encodes a serine hydroxymethyltransferase isoform. Since interspecies D NA comparison is a valuable tool for identifying sequences that have been c onserved because of their functional importance or role in regulating gene activity, mel-32(SHMT) genomic DNA from C. elegans was used to screen a gen omic library from the closely related nematode Caenorhabditis briggsae. The C. briggsae genomic clone identified fully rescues the Mel-32 phenotype in C. elegans, indicating functional and regulatory conservation. Computer an alysis reveals that CbMEL-32(SHMT) is 92% identical (97% similar) to CeMEL- 32(SHMT) at the amino acid level over the entire length of the protein (484 amino acids), whereas the coding DNA is 82.5% identical (over 1455 nucleot ides). Several highly conserved noncoding regions upstream and downstream o f the mel-32(SHMT) gene reveal potential regulatory sites that may bind tra ns-acting protein factors, (C) 1999 Published by Elsevier Science B.V. All rights reserved.