Molecular evolution of the mouse proline-rich protein multigene family. Insertion of a long interspersed repeated DNA element.

Proline-rich proteins (PRPs) in the salivary glands of mice, rats, and hamsters are encoded by tissue-specific inducible multigene families. Mouse PRP genes are located on chromosome 8, and transcription is dramatically induced (about 70-fold) by isoproterenol treatment. Clones containing two nonallelic PRP genes (MP2 and M14) were isolated from cosmid and phage libraries of CD-1 mouse genomic DNA. The cloned regions comprise a contiguous block of 77 kilobase pairs of the mouse genome. Restriction mapping established the physical lineage of PRP genes MP2 and M14, and they are tandemly arrayed. The DNA sequence analysis presented in this report suggests that genes M14 and MP2 (Ann, D. K., and Carlson, D. M. (1985) J. Biol. Chem. 260, 15863-15872) arose via a gene duplication of a common ancestor. Two major differences between M14 and MP2 were observed. PRP gene MP2 has 13 tandemly arrayed 42-nucleotide repeats in exon II, whereas M14 has 17 repeats, and PRP gene M14 has an insertion by transposition of a 2-kilobase pair member of the long interspersed repeated DNA (LINE) family (LIMd) into intron I. The evolution of this PRP multigene family has been dominated by intra-exonic amplification of repeating nucleotide units coding for these and other proline-rich repeated peptides and by gene duplication. The LIMd element gives rise to heterogenous EcoRI, BamHI, and HindIII restriction enzyme patterns, and this insertion is also present in BALB/c, C57BL/6J, and DBA/2J mice.