THE SIZE HETEROGENEITY OF HUMAN LYSYL OXIDASE MESSENGER-RNA IS DUE TOALTERNATE POLYADENYLATION SITE AND NOT ALTERNATE EXON USAGE

We have isolated the entire gene coding for human lysyl oxidase. Codin g and untranslated domains of human lysyl oxidase mRNA were found in 7 exons, distributed throughout approximately 14 kb of human genomic DN A. The appearance of exon sequences in lysyl oxidase mRNA in several h uman tissues was determined using a reverse transcriptase - PCR assay. In contrast to a previous report, this analysis has unambiguously sho wn that the size heterogeneity of lysyl oxidase mRNA was not due to al ternate usage of any of the exons of the lysyl oxidase gene. Moreover, DNA sequence analysis of the entire 3.8 kb 3'-untranslated region (UT R) within exon 7 revealed multiple poly-adenylation sites which were s hown to be differentially expressed in human skin fibroblasts. This di fferential usage of polyadenylation sites within the 3'-UTR explains t he appearance of multiple lysyl oxidase mRNAs of different sizes.