THE CLONING AND CHARACTERIZATION OF A CDNA-ENCODING XENOPUS-LAEVIS DNA-LIGASE-I

A cDNA clone coding for DNA ligase I (LigI) was isolated from a Xenopu s laevis oocyte cDNA library. The 3766-bp sequence showed a putative O RF capable of encoding a 1070-amino-acid protein whose overall identit y with two mammalian sequences is 63%. This identity, however, rises t o 72.5% in the C-terminal portion of the protein that contains the act ive site. Expression of the cDNA in a prokaryotic system produces a pr otein that is immunologically identical to LigI and can be adenylated. The 180-kDa size of the recombinant protein is similar to the LigI de tected in oocyte. Northern blot analysis of ovary and embryo RNAs reve aled the expression of two (4.1 and 6 kb) LigI transcripts.