The present invention is directed to a polynucleotide comprising open reading frames defining a coding region encoding a retinoblastoma binding protein (RBP-7) as well as regulatory regions located both at the 5' end and the 3' end of said coding region. The present invention also pertains to a polynucleotide carrying the natural regulation signals of the RBP-7 gene which is useful in order to express a heterologous nucleic acid in host cells or host organisms as well as functionally active regulatory polynucleotides derived from said regulatory region. The invention also concerns polypeptides encoded by the coding region of the RBP-7 gene. The invention also deals with antibodies directed specifically against such polypeptides that are useful as diagnostic reagents. The invention also comprises genetic markers, namely biallelic markers, that are means that may be useful for the diagnosis of diseases related to an alteration in the regulation or in the coding regions of the RBP-7 gene and for the prognosis/diagnosis of an eventual treatment with therapeutic agents, especially agents acting on pathologies involving abnormal cell proliferation and/or abnormal cell differentiation.