Cloning and characterization of a family of cDNAs from human histiocyte macrophage cells encoding an arginine-rich basic protein related to the 70 kDU1-snRNP splicing factor

This paper describes the cloning and characterization of five cDNA members of a novel family of mRNAs, termed hm-1, isolated from human U937 macrophag e cells. Two family members (clones 46 and 11) show complete mRNA features [including ribosome binding sites (RBS), polyadenylation signals, and poly( A) tails], and encode the same protein (designated HM-1), but differ substa ntially in their 5' untranslated regions. The three other cDNAs (clones 20, 60, and 38) appear to represent partial cDNAs. The protein sequences deduc ed from the five hm-1 cDNAs are identical (some truncated), except for one Trp --> Cys substitution. Full-length HM-1 is 246 amino acids long, has a p redicted MW of 29431, is rich in arginine residues, has a pI of 10.25, and a mean hydrophobicity index of -1.23. HM-1 contains no obvious hydrophobic N-terminal cleavable signal sequence, and no potential N-glycosylation site s, but does contain three highly conserved motifs present in U1-70K splicin g factors, and contains numerous C-terminal Arg/Asp and Arg/Glu dipeptides characteristic of "RD" family members that function as regulators of mRNA s plicing. Northern hybridizations indicate that hm-1 is a family of mRNAs di fferentially expressed in a variety of human tissues.