REGULATION OF COL1A1 EXPRESSION IN TYPE-I COLLAGEN PRODUCING TISSUES - IDENTIFICATION OF A 49-BASE-PAIR REGION WHICH IS REQUIRED FOR TRANSGENE EXPRESSION IN BONE OF TRANSGENIC MICE

Previous deletion studies using a series of COL1A1-CAT fusion genes ha ve indicated that the 625 bp region of the COL1A1 upstream promoter be tween -2295 and -1670 bp is required for high levels of expression in bone, tendon, and skin of transgenic mice, To further define the impor tant sequences within this region, a new series of deletion constructs extending to -1997, -1794, -1763, and -1719 bp has been analyzed in t ransgenic mice, Transgene activity, determined by measuring CAT activi ty in tissue extracts of 6- to 8-day-old transgenic mouse calvariae, r emains high for all the new deletion constructs and drops to undetecta ble levels in calvariae containing the -1670 bp construct, These resul ts indicate that the 49 bp region of the COL1A1 promoter between -1719 and -1670 bp is required for high COL1A1 expression in bone, Although deletion of the same region caused a substantial reduction of promote r activity in tail tendon, the construct extending to -1670 bp is stil l expressed in this tissue. However, further deletion of the promoter to -944 bp abolished activity in tendon. Gel mobility shift studies id entified a protein in calvarial nuclear extracts that is not found in tendon nuclear extracts, which binds within this 49 bp region, Our stu dy has delineated sequences in the COL1A1 promoter required for expres sion of the COL1A1 gene in high type I collagen-producing tissues, and suggests that different cis elements control expression of the COL1A1 gene in bone and tendon.