CHARACTERIZATION OF THE MURINE CYCLIN D2 GENE - EXON INTRON ORGANIZATION AND PROMOTER ACTIVITY/

Cyclin D2 is normally expressed in G(1) and promotes progression throu gh G(1) of the cell cycle. From a murine genomic library constructed w ith spleen DNA, two overlapping genomic clones of cyclin D2 were isola ted. These clones contain most of the exon of cyclin D2 except exon 5. Characterization of these clones revealed that murine cyclin D2 mRNA spans over 18 kb and 5 exons ranging from 149 to similar to 462 bp in length, and suggested that exon 5 may be at least >5 kb downstream fro m exon 4. Primer extension analysis of cyclin D2 mRNA isolated from mu rine activated T cells detected 5 putative sites of transcription init iation. These are located at -499, -417, -391, -373, and -349 relative to the translation start site, which is given as +1. No consensus seq uence for TATA box existed at an appropriate position within the promo tor region. Instead, several putative transcriptional factor binding s ites for C/EBP, PEA3, AP2, NF-Y, Sp1, c-Myc, GATA-1, AP1, v-Myb, and C REB were detected. The 5'-flanking region of the cyclin D2 gene up to nucleotide -945 shared about 61% sequence homology between mouse and h uman. Functional analysis of promoter activity of the 5'-flanking regi on of cyclin D2 suggested that the region -1,100 to -805 including C/E BP, PEA3, AP2, NF-Y, c-Myc, and Sp1 may have a major positive regulato ry activity for expression of cyclin D2.