CHARACTERIZATION AND CHROMOSOMAL LOCALIZATION OF THE CORNEA-SPECIFIC MURINE KERATIN GENE KRT1.12

Keratins are a group of water-insoluble proteins constituting paired a cidic and basic keratin molecules that form 10-nm intermediate filamen ts in epithelial cells. Expression of the K3/K12 keratin pair characte rizes the cornea-type differentiation. However, the mechanism that reg ulates this cornea-specific K12 expression remains unknown. To provide a better understanding of the cornea-specific expression, we have clo ned the K12 cDNA (Liu, C.-Y., Zhu, G., Westerhausen-Larson, A., Conver se, R., Kao, C. W.-C., Sun, T.-T., and Kao, W. W.-Y. (1993) Curr. Eye Res. 12, 963-974). In present studies, the murine K12 keratin gene (Kr t1.12) was isolated and characterized. The murine Krt1.12 gene spans 6 ,567 base pairs of genomic DNA, and the mRNA encoding K12 keratin is d istributed into eight exons. Chromosome mapping reveals that murine Kr t1.12 is located within the Krt1 complex of mouse chromosome 11. In ad dition to the production of authentic K12 mRNA, the Krt1.12 gene gives rise to several alternate poly(A)(+) RNAs by the use of alternative s plicing in intron 2, an alternative pro meter in intron 1, and/or both . Sequence analysis indicates that the transcripts derived from altern ative splicing and/or the alternative promoter do not have a long open reading frame for keratin or keratin-like molecules. It is not known whether these alternate K12 poly(A)(+) RNAs have any biological functi ons, e.g. regulation of K12 gene expression.