Multiple gamma-crystallins of the mouse lens: fractionation of mRNAs by cDNA cloning

Abstract

cDNAs made from polyadenylylated RNAs of the mouse lens were cloned by the G.C tailing procedure in the bacterial plasmid pBR322. Four recombinant DNAs containing gamma-crystallin sequences were identified by hybrid selection and translation. Sequence analysis of the in vivo-labeled gamma-crystallin polypeptides that cofocused isoelectrically with the hybrid-selected translation products established that the four cloned cDNAs were derived from mRNAs encoding gamma-crystallin polypeptides with similar NH2 termini. The cDNA clones had different restriction maps and could discriminate among the different gamma-crystallin mRNAs under stringent hybridization conditions. Under relaxed hybridization conditions, the cDNA clones cross-hybridized with all gamma-crystallin mRNAs, and even slightly with beta-crystallin mRNAs, as judged by in vitro translation. RNA blot hybridization showed that the mouse lens gamma-crystallin mRNAs are 840 +/- 100 nucleotides long. These data indicate that there are at least four similar gamma-crystallin mRNAs and suggest (but do not establish) the existence of a closely related family of gamma-crystallin genes.