Chromatin assembly factor 1 ensures the stable maintenance of silent chromatin states in Arabidopsis

Abstract

Newly synthesized DNA is rapidly assembled into mature nucleosomes by the deposition of preexisting and nascent histones, and some parts of this process are facilitated by chromatin assembly factor 1 (CAF-1). Loss-of-function mutants of CAF-1 in Arabidopsis , fasciata ( fas ), show a variety of morphological abnormalities and unique defects in gene expression in the meristems. In order to clarify the implications of CAF-1 in the maintenance of chromatin states in higher eukaryotes, we investigated transcriptional gene silencing (TGS) of various genes in fas mutants. Here, we show that TGS of endogenous CACTA transposons was released in a stochastic manner in fas . Other endogenous silent genes, a transposon AtMu1 and a hypothetical gene T5L23.26 at a heterochromatin knob, were also transcriptionally activated, and the activation of the three different silent loci at different chromosomal sites occurred non-concomitantly with each other. Furthermore, TGS of the silent β β β β -glucuronidase ( GUS ) transgene was also de-repressed randomly in fas . We conclude that CAF-1 ensures the stable inheritance of epigenetic states through growth and development in Arabidopsis .

E2F RegulatesFASCIATA1, a Chromatin Assembly Gene Whose Loss Switches on the Endocycle and Activates Gene Expression by Changing the Epigenetic Status

“…In addition, they showed that CAF-1 is dispensable for maintenance of DNA methylation. In another report, transcriptional silencing of the endogenous CACTA transposon is relieved in fas mutants (Ono et al, 2006), although this transcriptional activation was relatively weak, infrequent, and stochastic. We have found that transcriptional activation of a set of euchromatin genes is not due to global changes in chromatin organization over large chromosomal regions.…”

The second subunit of DNA-polymerase delta is required for genomic stability and epigenetic regulation

“…Other studies have identified other DNA replication-related proteins involved in mediating TGS, including BRU1 (Takeda et al, 2004), chromatin assembly factor (CAF-1) subunits FAS1 and FAS2 (Ono et al, 2006;Schonrock et al, 2006), and TEBICHI (Inagaki et al, 2009). The release of TGS by defects in the DNA-replication machinery suggests that these processes must have a common mechanism.…”

Chromatin remodeling in plant development

“…CAF1 seems to be necessary to ensure the stable inheritance and maintenance of epigenetic states during DNA replication (Kaya et al, 2001). Indeed, fas1 mutants display a stochastic release of Transcriptional Gene Silencing (TGS) and overexpression of genes located in heterochromatic genomic regions (Ono et al, 2006). In addition, the expression of stem-cell regulatory genes such as WUS is severely altered (Figure 1; Kaya et al, 2001).…”

“…This is the case of mutants altered in the Chromatin-Assembly Factor-1 (CAF1), a histone-binding protein complex which participates in de novo nucleosome assembly during DNA replication (Ramírez-Parra and Gutiérrez, 2007). CAF1 is formed by three subunits conserved in all eukaryotes that in Arabidopsis are encoded by FASCIATA1 (FAS1), FAS2 and MULTICOPY SUPPRESSOR OF IRA1 (MSI1) (Kaya et al, 2001;Hennig et al, 2003;Kirik et al, 2006;Ono et al, 2006). CAF1 seems to be necessary to ensure the stable inheritance and maintenance of epigenetic states during DNA replication (Kaya et al, 2001).…”