CORRELATION OF THE STEADY-STATE RNA LEVELS AMONG THE ALPHA-SUBUNIT OF PROLYL 4-HYDROXYLASE AND THE ALPHA-1 AND ALPHA-2 CHAINS OF TYPE-I COLLAGEN DURING GROWTH OF CHICKEN-EMBRYO TENDON FIBROBLASTS

The relative steady-state levels of RNAs encoding type I collagen and prolyl 4-hydroxylase were examined in exponentially growing primary cultures of chicken embryo tendon fibroblasts. The RNA levels of the α1 and α2 chains of type I collagen were maximal when the fibroblasts reached the confluent state. The RNA levels of the α-subunit of prolyl 4-hydroxylase were also maximal at confluency and rose and fell with the RNA levels of the two collagen chains. The RNA levels of the β-subunit of prolyl 4-hydroxylase did not correlate with the changes observed for the α-subunit or for either chain of type I collagen. The RNA levels of the β-subunit were slightly higher than the RNA levels of the α-subunit. These results support our hypothesis that the synthesis of the α-subunit and thus the association of newly synthesized α-subunits with pre-existing β-subunits is the rate-limiting factor in determining prolyl 4-hydroxylase activity in cultured cells. © 1991.