THE GENE STRUCTURE AND ORGANIZATION OF MOUSE PG-M, A LARGE CHONDROITIN SULFATE PROTEOGLYCAN - GENOMIC BACKGROUND FOR THE GENERATION OF MULTIPLE PG-M TRANSCRIPTS

We previously showed not only the presence of multiple RNA transcripts of different sizes encoding the core protein of mouse PG-M, but also their tissue-dependent expression, Major causes for the multiple forms were found to be due to alternative usage of the two different chondr oitin sulfate attachment domains (alpha and beta). In this study, geno mic DNA analysis has revealed that these domains are encoded by two la rge exons, exon VII (2880 base pairs) and exon VIII (5229 base pairs), The splice sites of these two exons were consistent with the occurren ce of alternative splicing without frameshift. Furthermore, the mouse PG-M gene was shown to have four distinct polyadenylation signals and three candidates for the transcription initiation site as well. These genomic structural variations may contribute to the multiplicity of PG -M transcripts. Northern hybridization analysis showed that at least t hree different transcripts were generated by different usage of the di stinct polyadenylation signals.