Two forms of messenger RNA encoding rat liver mannan-binding protein are generated by differential utilization of polyadenylation sites of one transcript.

Rat liver mannan-binding protein (R-L-MBP) is a lectin specific for mannose and N-acetylglucosamine. Northern blot hybridization analysis with a R-L-MBP cDNA (0.9 kb), which we isolated previously [Oka, S., Itoh, N., Kawasaki, T., & Yamashina, I. (1987) J. Biochem. 101, 135-144], revealed that R-L-MBP was encoded by two species of mRNA of 1.4 and 3.5 kb long, respectively. Analysis of a newly isolated cDNA clone of 3.3 kb long showed that the sequence of the open reading frame of the 3.5 kb mRNA was completely identical to that of the 1.4 kb mRNA. The 3'-untranslated region of the 3.5 kb mRNA contained two inverted copies of the previously described identifier (ID) sequence, which is a repetitive element of the rat genome [Milner, R.J., Bloom, F.E., Lai, C., Lerner, R.A., & Sutcliffe, J.G. (1984) Proc. Natl. Acad. Sci. U.S.A. 81, 713-717]. Southern blot analysis of rat genomic DNA digested with restriction enzymes suggested that each mRNA species arises from one gene, with the differences in size most easily being accounted for by differential utilization of the polyadenylation sites of one transcript.