A conserved family of WD-40 proteins binds to the retinoblastoma protein in both plants and animals.

Abstract

In mammalian cells, the retinoblastoma (RB) protein regulates G , progression and functions through its association with various cellular proteins. Two closely related mammalian RB binding proteins, RbAp48 and RbAp46, share sequence homology with the Msil protein of yeast. MSll is a multicopy suppressor of a mutation in the lRA1jgene involved in the Ras-cAMP pathway that regulates cellular growth. Human RbAp48 is present in protein complexes involved in histone acetylation and chromatin assembly. We report the cloning of cDNAs encoding four plant RbAp48-and Msil -like proteins: one from tomato, LeMSIf, and three from Arabidopsis. Complementation studies confirm that LeMSl7 can function as a multicopy suppressor of the yeast ira1 mutant phenotype. The LeMSI1 protein localizes to the nucleus and binds to a 65-kD protein in wild-type as well as ripening inhibitor (rin) and Neverripe (Nr) tomato fruit. LeMSll also binds to the human RB protein and the RB-like RRBl protein from maize, indicating that this interaction is conserved between plants and animals.

The Female Gametophyte and the Endosperm Control Cell Proliferation and Differentiation of the Seed Coat inArabidopsis

“…MSI1 and other FIS genes encode the four members of the conserved core of the class 2 Polycomb group complex (Grossniklaus et al, 1998;Ohad et al, 1999;Luo et al, 2000;Kö hler et al, 2003;Guitton et al, 2004). It was shown that FIE and MIS1 interact with the RETINOBLASTOMA-RELATED homolog RBR1 in Arabidopsis (Mosquna et al, 2004) and other plants (Ach et al, 1997). Supporting this interaction, spontaneous nuclear proliferation has been observed in female gametophytes in the absence of fertilization of the rbr1 mutant in Arabidopsis (Ebel et al, 2004).…”

Impact of nucleosome dynamics and histone modifications on cell proliferation during Arabidopsis development

“…These mechanisms contribute to recruit HDAC to E2F-bound promoters at early G1 and maintain their repressed state (Ferreira et al, 2001;Rayman et al, 2002). Plants seem to share this mechanism, as it has been experimentally demonstrated in maize and tomato (Ach et al, 1997;Nicolas et al, 2001;Rossi et al, 2001;Rossi and Varotto, 2002).…”

“…Interestingly, the tumor suppressor Retinoblastoma protein (Rb) is necessary to maintain H3K27 methylation and PRC2 and PRC1 binding to the promoter of the CDK inhibitor p16 in human cells (Kotake et al, 2007). The plant homolog of human Rb, the RETINOBLASTOMA-RE-LATED (RBR) protein, binds to FIE (Mosquna et al, 2004) and MSI1 (Ach et al, 1997;Rossi et al, 2001). Although these interactions have not been demonstrated yet in planta, it is tempting to speculate that RBR may be one candidate involved in PRC2 recruitment to the promoter of a subset of target genes.…”

Histone chaperones in nucleosome eviction and histone exchange

“…The structures of several variants of nucleoplasmin ( [42] and references therein), NAP1 and the related SET/TAF-1 [43] [44] (all putative H2A/H2B chaperones) are now known, as is the structure of the H3-H4 chaperone Asf1 [45]. The structures of HIRA and the histone binding subunit of CAF-1 have been predicted through homology modeling [46,47]. These studies have revealed no similarities in the overall fold or oligomerization state of histone chaperones.…”