Specific mouse liver cDNA clones

Abstract

Several liver secretory protein cDNAs were isolated from a female BALB/c mouse liver cDNA library. The mouse major urinary proteins (MUPs) are encoded within a multigene family of about 35 genes. Most MUPs are members of either Group 1 or Group 2 sequences, which can be distinguished by DNA sequence divergence. Two of the sequenced clones, MUP 8 and MUP 11 were of the Group 1 type. A third MUP clone, MUP 15, has diverged from both Group 1 and Group 2 sequences (i.e. BS 6 and BS 2,3) by 15% and 17.4% respectively. The divergence is twice as great over exons 1-3 and the 3' terminal 68 nucleotides of the comparison, as it is over the intervening sequence. This suggests that an ancestral conversion event has occurred. MUP 15, like some Group 2 genes, has a longer signal peptide than Group 1 genes and differs from both Groups in having a probable N-linked glycosylation site and a different splice configuration between exons 6 and 7.

Transferrin is the major iron binding protein in vertebrate serum. Transferrin cDNA clones corresponding to 1.16 Kb of the 3'half of the mRNA were isolated. The clones were identical where they overlapped, which implies that there is one predominantly expressed transferrin gene in mouse liver.

Comparison of the mouse exonic sequence with human and chicken transferrins showed 18.0% and 35.5% replacement and 38.4% and 99.0% silent site divergence respectively. There are also small areas of higher homology within the domains, which may define iron binding sites. Preliminary investigations into two other cDNA clones are discussed. These correspond to the 3' end (950 Bp) of the third component of mouse complement and the N-terminal half, (810 Bp) of mouse contrapsin, which is homologous to human alpha^- antichymotrypsin.