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Histone Methylation and Incorporation-into-nucleosome in Epigenetic Regulation and Inheritance in Arabidopsis Thaliana

出版	2011
URL	http://books.google.com.hk/books?id=ILZungEACAAJ&hl=&source=gbs_api

註釋The SET domain proteins are recognized as generally having histone methyltransferase activity. I showed that the recombinant SDG25 protein could methylate in vitro histone H3 using oligonucleosomes as a substrate. Using T-DNA insertion lines, we showed that loss-of-function of SDG25 caused an early-flowering phenotype associated with a reduced level of FLC expression. Our results establish a function for the previously uncharacterized gene SDG25 in the FLC activation and flowering time regulation.Nucleosome Assembly Protein 1 (NAP1) represents the primary chaperone of H2A and H2B. The Arabidopsis genome contains 6 genes encoding NAP1 homolgoues belonging to two phylogenic groups: NAP1-subgroup and NRP-subgroup. The two allelic triple mutants m123-1 and m123-2 exhibit perturbed genome transcription and show hypersensitivity to DNA damage caused by UV-C irradiation. Furthermore, we found that the Atnap1;3-2 allele expresses a truncated protein, AtNAP1;3-T, which lacks 34 amino acids at the C-terminus. We showed that AtNAP1;3-T is related to ABA-hyposensitive and Salt-hypersensitive tress phenotype.. Our work indicates that AtNAP1 proteins can function as modulators of chromatin structure in response to different environmental stresses.Homologous recombination (HR) is important for DSB repair in all eukaryotes. Using GUS-based recombination substrates, I demonstrated that somatic HR is impaired in m123-1 and m123-2 as well as nrp1-1nrp2-1 mutant plants under standard or divers stress growth conditions, and that nrp1-1nrp2-1 dominates fas2-4 specifically in HR in a way that the nrp1-1nrp2-11fas2-4 plants exhibit a low HR similar to nrp1-1nrp2-1 but a morphological phenotype largely similar to fas2-4. It is very tempting to speculate that AtNAP/NRP proteins contribute to initial steps such as extensive end resection after DSB, strand invasion and heteroduplex extension during HR.