Studies on genetic variation in major urinary protein synthesis in mouse liver.

A two- to fourfold difference in the relative rate of total major urinary protein (MUP) synthesis between C57BL/6J and C3H/HeJ female mice has been analyzed at the genetic and molecular levels. The C57BL/6J phenotype is dominant in F1 female progeny of a cross between the two strains. Quantitation of MUP mRNA levels indicates that the rate of synthesis variation does not reflect a change in the concentration of total MUP mRNA. In recombinant inbred strains derived from C57BL/6J and C3H/HeJ progenitors, the rate of synthesis difference segregates as a single genetic determinant that is not linked to the Mup-a locus on chromosome 4. The results suggest an unlinked locus that acts to alter total MUP synthesis without altering total MUP mRNA levels. Two models are proposed to describe the action of this locus, both of which imply some sort of posttranscriptional control of MUP synthesis.