Abnormal expression of the RI subunit of cyclic AMP-dependent protein kinase in Y-79 retinoblastoma cells.
The cyclic AMP-dependent protein kinases of Y-79 retinoblastoma cells were analyzed by DEAE Sephacel column chromatography, SDS-polyacrylamide gel electrophoresis, and immunoblotting. Both type I and type II protein kinases (characteristic of fetal and mature retina respectively) were observed. In addition, free RI (type I regulatory subunit) was present in Y-79 cells; three other retinoblastoma cell lines also showed evidence of free RI in immunoblot analysis. Northern blot analysis of poly A+-enriched RNA from Y-79 cells showed a 4.5 kb RI transcript and a 6.0 kb RII transcript. The single 4.5 kb RI message is typical of normal retina, in contrast to other tissues and cell lines in which a 2.0 kb message predominates. Since RI expression appears to be post-transcriptionally inhibited in normal retina, it is suggested that free RI dimers in retinoblastoma is the result of loss of repression of translation of this transcript and that the free RI pool may contribute to the unregulated growth of these cells.
Gentleman
S
S
Laboratory of Retinal Cell and Molecular Biology, National Institutes of Health, Bethesda, Maryland 20892.
Russell
P
P
Hemmings
B A
BA
Chader
G J
GJ
D002460:Cell Line; D005134:Eye Neoplasms / Q000201:enzymology*; D006801:Humans; D007527:Isoenzymes / Q000302:isolation & purification; D011494:Protein Kinases / Q000302:isolation & purification*; D012175:Retinoblastoma / Q000201:enzymology*; D014407:Tumor Cells, Cultured / Q000201:enzymology
D007527:Isoenzymes; D011494:Protein Kinases