A WD40 Domain Cyclophilin Interacts with Histone H3 and Functions in Gene Repression and Organogenesis inArabidopsis

Abstract

Chromatin-based silencing provides a crucial mechanism for the regulation of gene expression. We have identified a WD40 domain cyclophilin, CYCLOPHILIN71 (CYP71), which functions in gene repression and organogenesis in Arabidopsis thaliana. Disruption of CYP71 resulted in ectopic activation of homeotic genes that regulate meristem development. The cyp71 mutant plants displayed dramatic defects, including reduced apical meristem activity, delayed and abnormal lateral organ formation, and arrested root growth. CYP71 was associated with the chromatin of target gene loci and physically interacted with histone H3. The cyp71 mutant showed reduced methylation of H3K27 at target loci, consistent with the derepression of these genes in the mutant. As CYP71 has close homologs in eukaryotes ranging from fission yeast to human, we propose that it serves as a highly conserved histone remodeling factor involved in chromatin-based gene silencing in eukaryotic organisms.

AtFKBP53 is a histone chaperone required for repression of ribosomal RNA gene expression in Arabidopsis

“…It is speculated that changes in chromatin structure often bring about global changes in expression of many genes. For example, AtCYP71 in plants clearly has such a global role and the cyp71 mutant plants showed a number of developmental defects caused possibly by de-repression of many genes [31]. In this report, we show that AtFK-BP53 associates with 18S rDNA chromatin and regulates the level of its expression.…”

“…In vitro pull-down assays were performed as described previously with modifications [31]. Purified recombinant GSTAtFKBP53, GST-AtFKBP53-N1, GST-AtFKBP53-N2, GSTAtFKBP53-C1 or GST (1.5 µg) was immobilized to glutathione Sepharose beads at 4 °C for 2 h in the A300 binding buffer.…”

“…Furthermore, SpFkbp39p and Fpr4 were identified as acidic histone chaperones in S. pombe and S. cerevisiae, respectively [7,30]. In plants, Arabidopsis AtCYP71, a member of cyclosporine A binding proteins (cyclophilins, CYPs), was also shown to interact with histone H3 and regulate gene expression pattern that determines the development of Arabidopsis [31]. Analysis of these factors suggested that nuclear immunophilins might contribute to the dynamics of chromatin complex assembly and/or disassembly because they interact with basic chromatin components.…”

Master and servant: Regulation of auxin transporters by FKBPs and cyclophilins

“…TWD1 also possesses a tetratricopeptide repeat domain (common [131] Regulation and PM-to-ER trafficking of ABCB-type auxin transporters [8,9] Z. mais [133] Interaction with ABCB transporters on PM (via FKB-domain) [8,62], ABCC transporters on tonoplast (via TPR domain) [66], with HSP90 (TPR domain) [62,65] and calmodulin (calmodulin-binding domain) [66] Over-expression of TWD1 lacking its membrane anchor results in hypermorphic growth [64] FKBP72/PAS1 A. thaliana [69] Unclear (C-terminal membrane anchor), nuclear [68,134] Low, inhibited by FK506 and rapamycin [134] Up-regulated cell division, leaf fusions, short hypocotyls, sterile [69] O. sativa [131] Chaperon during translocation of NAC-like transcription factor (AtFAN) into nucleus [68] Z. mais [133] Regulation of very long fatty acid elongation [70] -DGT/CypA/ROC1/CYP1/CYP2/ P. patens [10] Nuclear and cytoplasmic [10,90], phloem sieve elements [79] Significant [77,78], inhibited by CsA [78] Regulates growth [90], gene expression [84,90,92], patterned cell division [88], phloem function [79], ROS balance in root apical meristem [87] A. [137] in many large immunophilins) that was shown to interact with vacuolar ABC transporters of the C subclass and HSP90 [65,66], as well as a calmodulin-binding domain [66] (see Fig. 1).…”

The CURLY LEAF Interacting Protein BLISTER Controls Expression of Polycomb-Group Target Genes and Cellular Differentiation ofArabidopsis thaliana

“…bli-1 mutants also display other severe defects in organ patterning, cellular identity, and differentiation: vascular strands are frequently unconnected and trichome numbers and patterning are altered in bli-1 (Figures 5 and 6). Vascular development is controlled by many different pathways, including an important role of the phytohormone auxin (reviewed in Sieburth and Deyholos, 2006), but also cyclophilin71 mutants, which are possibly linked to Pc-G silencing display similar alterations (Li et al, 2007). As cell size at least in the cotyledon epidermis is also strongly increased, cell numbers are decreased and a higher level of endoreduplication is observed in bli-1 mutants (Figure 6), this reveals an important role for BLI to prevent premature cellular differentiation and promote cell division.…”