Regulation of EPC-1/PEDF in normal human fibroblasts is posttranscriptional.
The EPC-1 (early population doubling level cDNA-1) gene, also known as pigment epithelium-derived factor, encodes a protein belonging to the serine protease inhibitor (serpin) superfamily that has been reported to inhibit angiogenesis and proliferation of several cell types. We have previously reported that the EPC-1 mRNA and the secreted EPC-1 protein are expressed at levels more than 100-fold higher in early passage, G(0), WI-38 cells compared to either proliferating or senescent WI-38 fibroblasts. To examine the molecular mechanisms that regulate changes in EPC-1 gene expression in WI-38 cells, we isolated and characterized the human EPC-1 gene and determined the mRNA cap site. Transcriptional assays showed no change in the transcription rates of EPC-1 between young proliferating, quiescent, and senescent WI-38 cells. These results suggest posttranscriptional regulation of the EPC-1 gene. Reverse transcriptase polymerase chain reaction measurements (of hnRNA) indicate regulation at the hnRNA level. The regulation of the EPC-1 gene at the level of hnRNA can explain the observed slow increase in the steady-state EPC-1 mRNA levels when cells become quiescent. The reduction of EPC-1 mRNA levels that occurs when cells exit G(0) and are induced to proliferate can be accounted for by a reduction of the EPC-1 mRNA stability in stimulated cells as compared to quiescent cells.
Coljee
V W
VW
Center for Gerontological Research, Allegheny University of the Health Sciences, Philadelphia, Pennsylvania 19129, USA.
Rotenberg
M O
MO
Tresini
M
M
Francis
M K
MK
Cristofalo
V J
VJ
Sell
C
C
D000818:Animals; D015152:Blotting, Northern; D002417:Cattle; D002455:Cell Division; D002460:Cell Line; D016922:Cellular Senescence; D003470:Culture Media / Q000494:pharmacology; D016895:Culture Media, Serum-Free; D005136:Eye Proteins; D005312:Fetal Blood / Q000502:physiology; D005347:Fibroblasts / Q000187:drug effects* / Q000378:metabolism; D016762:Genes, fos; D006801:Humans; D009414:Nerve Growth Factors; D011401:Promoter Regions, Genetic; D014176:Protein Biosynthesis; D011506:Proteins / Q000235:genetics; D012323:RNA Processing, Post-Transcriptional / Q000187:drug effects; D012332:RNA, Heterogeneous Nuclear / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015843:Serpins / Q000096:biosynthesis* / Q000235:genetics; D000099174:Pigment Epithelium-Derived Factor
D003470:Culture Media; D016895:Culture Media, Serum-Free; D005136:Eye Proteins; D009414:Nerve Growth Factors; D011506:Proteins; D012332:RNA, Heterogeneous Nuclear; D012333:RNA, Messenger; D015843:Serpins; D000099174:Pigment Epithelium-Derived Factor