Dephosphorylation of the retinoblastoma gene product induced by differentiation and its relevancy to growth inhibition in normal human keratinocytes.
The retinoblastoma gene product (pRB) is a tumor suppressor gene product. Recently, it has been shown that the dephosphorylation of pRB leads a variety of cells into G1/G0 arrest. Keratinocytes were grown in serum-free MCDB 153 medium containing 0.1 mM Ca2+, followed by addition of Ca2+ to 1.8 mM (calcium switch). Under-phosphorylated pRB band appeared at 48 h and increased up to 72 h after calcium switch. S phase cells decreased at 48 and 72 h in a time-dependent manner. In contrast, the number of involucrin positive cells, differentiated cells, increased even at 24 h, preceding the dephosphorylation of pRB and continued to increase up to 72 h. These results indicate that the dephosphorylation of pRB is closely related to growth inhibition of human keratinocytes associated with differentiation.
Kobayashi
T
T
Department of Dermatology, Osaka University School of Medicine, Japan.
Hashimoto
K
K
Yoshikawa
K
K
D002118:Calcium / Q000494:pharmacology; D002453:Cell Cycle / Q000502:physiology; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D016193:G1 Phase / Q000502:physiology; D015870:Gene Expression; D016161:Genes, Retinoblastoma / Q000235:genetics*; D006801:Humans; D015603:Keratinocytes / Q000166:cytology* / Q000378:metabolism*; D010766:Phosphorylation; D011498:Protein Precursors / Q000009:adverse effects / Q000235:genetics; D016192:Resting Phase, Cell Cycle / Q000502:physiology; D016160:Retinoblastoma Protein / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D016196:S Phase / Q000502:physiology; D013997:Time Factors
D011498:Protein Precursors; D016160:Retinoblastoma Protein; C032253:involucrin; D002118:Calcium