Retinoblastoma-Related Protein 1 (RBR1) Arabidopsis Thaliana Recombinant Protein

Encodes a retinoblastoma homologue RETINOBLASTOMA-RELATED protein (RBR or RBR1). RBR controls nuclear proliferation in the female gametophyte. Also required for correct differentiation of male gametophytic cell types. Regulates stem cell maintenance in Arabidopsis roots. Involved in the determination of cell cycle arrest in G1 phase after sucrose starvation. RBR1 is also involved in regulation of imprinted genes. Together with MSI1 it represses the expression of MET1. This in turn activates expression of the imprinted genes FIS2 and FWA. Functions as a positive regulator of the developmental switch from embryonic heterotrophic growth to autotrophic growth

Key regulator of entry into cell division. Acts as a transcription repressor of E2F target genes, whose activity is required for progress from the G1 to the S phase of the cell cycle. Hyperphosphorylation by CDKA-1 prevents the binding to E2F transcription factors, allowing G1 to S phase transition to operate (PubMed:18064404, PubMed:21444209). Forms a stable complex with E2FA that functions in maintaining cell proliferation through repression of cell differentiation (PubMed:22307083). Plays a central role in the mechanism controlling meristem cell differentiation, cell fate establishment and cell fate maintenance during organogenesis and gametogenesis (PubMed:16377572, PubMed:16815954, PubMed:19359496, PubMed:20525851, PubMed:20585548, PubMed:20683442, PubMed:22595674, PubMed:24285791, PubMed:25303364). Required during lateral organ production (PubMed:20525851). Also involved in controlling asymmetric divisions of stem cells in different stem cell niches (PubMed:22921914, PubMed:23104828, PubMed:24302889). Acts as negative regulator of cell proliferation during leaf and gametophytes development (PubMed:15201912, PubMed:16361519, PubMed:18976913). At later stages of development, restricts the progression through additional endocycles (PubMed:16361519). In the leaf, plays a role in the control of the mesophyll differentiation (PubMed:24118480). Another role is its implication in the regulation of imprinted genes. Acts together with MSI1 to repress the expression of MET1 during gametogenesis. This in turn activates expression of the imprinted genes FIS2 and FWA (PubMed:18700816). Regulates many genes of the polycomb repressive complex 2 (PRC2) (PubMed:18976913, PubMed:19704913, PubMed:20585548). Plays an important role in meiosis affecting different aspects of this complex process (PubMed:21217641). Functions as a positive regulator of the developmental switch from embryonic heterotrophic growth to autotrophic growth (PubMed:21693514). Interaction with mastrevirus RepA or nanovirus Clink protein disrupts the RBR/E2F interaction and releases the transcription of replicative enzymes needed by the virus by increasing the E2F DNA-binding activity (PubMed:16361519).