Insulin-like growth factor II promoter expression in cultured rodent osteoblasts and adult XXXX bone.

@entity2620 @entity664 @entity19 @entity1810 @entity35
@entity2620 stimulates bone formation by increasing the replication of cells of the osteoblastic lineage and by enhancing the differentiated function of the osteoblast. Although @entity2620 is synthesized by skeletal cells, little is known about the mechanisms involved and its regulation by growth factors. @entity2620 expression is tissue specific and is developmentally regulated. In the present study, we examined the expression of @entity2620 in fetal @entity35 , newborn @entity19 and @entity19 osteoblastic (Ob) cells, and in adult @entity35 calvariae. We also determined mechanisms involved in the regulation of @entity2620 by platelet-derived growth factor (PDGF) BB, @entity664 ( @entity664 ), and @entity1810 . Northern analysis revealed @entity2620 transcripts of 3.6 and 1.2 kb in osteoblastic cells and adult @entity35 calvariae. Ribonuclease (RNase) protection assay using probes specific to the three known @entity2620 promoters, P1, P2, and P3, demonstrated messenger RNA (mRNA) expression driven by P3 in osteoblasts and adult @entity35 calvariae, but no expression of P1 or P2 transcripts. PDGF BB, @entity664 , and @entity1810 inhibited the expression of @entity2620 P3 mRNA by 50%. PDGF BB, @entity664 , and @entity1810 also decreased the rates of @entity2620 transcription in @entity35 Ob cells as determined by nuclear run-on assays and did not modify the decay of @entity2620 in transcriptionally arrested @entity35 Ob cells. In conclusion, the synthesis of @entity2620 in osteoblastic cells and in adult @entity35 calvariae is driven by @entity2620 P3 and is regulated by skeletal growth factors acting at the transcriptional level using the @entity2620 P3.
