CLONING OF A CDNA-ENCODING SHEEP CALCITONIN FROM A THYROID C-CELL LIBRARY

A sheep thyroid C-cell cDNA library constructed in lambdaZAPII was scr eened with a probe specific for the human calcitonin (CT)-encoding gen e (CT). Plaque lifts from a total of 6 x 10(4) recombinant plaques ide ntified six overlapping cDNA clones, one of which was an 806-bp cDNA r epresenting an almost full-length copy of the sheep CT mRNA. The nucle otide (nt) sequence consists of a 71-bp 5'-flanking sequence, a protei n-coding region of 429 bp with a coding potential for a 143-amino-acid (aa) protein with a deduced M(r) of 15 888 and a 306-bp 3'-untranslat ed region. Northern blot analysis of sheep thyroid tissue revealed two major mRNAs with sizes of 0.9 and 0.65 kb. The sheep CT cDNA shows 71 % similarity at the nt level to human CT and 58% identity at the predi cted aa level.