TRANSCRIPTION BY RNA-POLYMERASE-I AND RNA-POLYMERASE-III - A POTENTIAL LINK BETWEEN CELL-GROWTH, PROTEIN-SYNTHESIS AND THE RETINOBLASTOMA PROTEIN

The rate of protein synthesis is a critical determinant of cellular gr owth. Abnormal activation of this process is a frequent feature of tra nsformed and tumour cells. Several distinct components of the translat ion apparatus have been shown to be deregulated in response to maligna nt transformation. Indeed, overexpression of certain translation facto rs has been found to predispose cells to transformation or even initia te it. The latest twist to this story comes from the discovery that th e retinoblastoma protein RE plays a major role in restricting the prod uction of tRNA and rRNA. RB is an important tumour suppressor, Its abi lity to limit the synthesis of these principle determinants of biosynt hetic capacity could provide a mechanism for restraining cell growth, The loss of this control may constitute a significant step towards tum our progression.