Cloning and sequence analysis of a cDNA coding for the murine DNA ligase I enzyme

A complementary DNA (2961 bp) containing the complete coding sequence for murine DNA ligase I was isolated from a mouse fibroblast cDNA library using a cDNA encoding the human protein as a probe. An open reading frame of 2748 bp, encoding a protein of 916 amino acids (aa), was identified. Northern blot analysis of total RNA extracted from mouse fibroblasts showed a single band with a mobility corresponding to a size of 3.2 kb whose level increases upon serum stimulation of quiescent mouse NIH-3T3 cells. Alignment of the murine and human deduced aa sequences showed an overall 83% identity, that rises to 91% if only the sequence on the C-terminal portion of the protein containing the active site is considered.