The PHD finger protein 1 (PHF1) is essential in epigenetic regulation and genome maintenance. Here, we demonstrate that the Tudor domain of human PHF1 binds to histone H3 trimethylated at Lys36 (H3K36me3). We report a 1.9 Å resolution crystal structure of the Tudor domain in complex with H3K36me3 and describe the molecular mechanism of H3K36me3 recognition using NMR analysis. Binding of PHF1 to H3K36me3 inhibits the ability of the Polycomb PRC2 complex to methylate H3K27 in vitro and in vivo. Laser micro-irradiation data reveal that PHF1 is transiently recruited to DNA double-strand breaks (DSBs), and PHF1 mutants impaired in the H3K36me3 interaction exhibit reduced retention at DSB sites. Together, our findings suggest that PHF1 can mediate deposition of the repressive H3K27me3 mark and acts as an early DNA damage response cofactor.

DNA damage causes genome instability and cell death, but many of the cellular responses to DNA damage still remain elusive. We here report a human protein, PALF (PNK and APTX-like FHA protein), with an FHA (forkhead-associated) domain and novel zinc-finger-like CYR (cysteinetyrosine-arginine) motifs that are involved in responses to DNA damage. We found that the CYR motif is widely distributed among DNA repair proteins of higher eukaryotes, and that PALF, as well as a Drosophila protein with tandem CYR motifs, has endo-and exonuclease activities against abasic site and other types of base damage. PALF accumulates rapidly at single-strand breaks in a poly(ADPribose) polymerase 1 (PARP1)-dependent manner in human cells. Indeed, PALF interacts directly with PARP1 and is required for its activation and for cellular resistance to methyl-methane sulfonate. PALF also interacts directly with KU86, LIGASEIV and phosphorylated XRCC4 proteins and possesses endo/exonuclease activity at protruding DNA ends. Various treatments that produce double-strand breaks induce formation of PALF foci, which fully coincide with cH2AX foci. Thus, PALF and the CYR motif may play important roles in DNA repair of higher eukaryotes.

Oedometer tests starting from a very small effective vertical stress of 0.5 kPa were performed on three reconstituted clays with different liquid limits. The soils were prepared at various initial water contents, ranging from 0.7 to 2.0 times their corresponding liquid limits. It is observed that the e-logσ v´ compression curves show an inverse "S" shape due to suction pressure resisting deformation, similar to that of soft natural clays caused by consolidation yield stress. The suction pressure σ s´ of the reconstituted clays can be correlated with the ratio of initial void ratio to void ratio at liquid limit e 0 /e L . The suction pressure curve (SPC) defined by a unique relationship between suction pressure σ s´ and the normalised void ratio at suction pressure e s /e L is also proposed to distinguish between the pre-suction and the post-suction states. In addition, Burland's concept of intrinsic compression line (ICL) is adopted for correlating the compression curves of various reconstituted clays at high initial water contents. It has been found that the void index is a powerful parameter for normalising the compression curves in the post-suction state. Nevertheless, it seems that Burland's ICL slightly underestimates the void index at the low stresses considered in this study. An extended intrinsic compression line (EICL) is then derived in order to better fit the data for stresses lower than 25 kPa. KEYWORDS: reconstituted clays; compressibility; initial water content; liquid limit; soil properties; suction pressure NOTATION C c * = (e * 100 -e * 1000 ) e = void ratio e 0 = initial void ratio e * 100 = void ratio of reconstituted clays at σ v ' = 100kPa e * 1000 = void ratio of reconstituted clays at σ v ' = 1000kPa e L = void ratio at liquid limit e s = void ratio at suction pressure EICL = extended intrinsic compression line ICL = intrinsic compression line I v = void index PI = plasticity index pre-suction state = effective vertical stress is smaller than suction pressure post-suction state = effective vertical stress is larger than suction pressure r = coefficient of correlation SPC = suction pressure curve w L = liquid limit w P = plastic limit w 0 = initial water content σ v ' = effective vertical stress σ s ' = suction pressure 3 INTRODUCTIONMany studies have been carried out to assess the in-situ mechanical behaviour of natural sedimentary soils (e.g.

DNA double-strand breaks (DSBs) represent the most toxic DNA damage arisen from endogenous and exogenous genotoxic stresses and are known to be repaired by either homologous recombination or nonhomologous end-joining processes. Although many proteins have been identified to participate in either of the processes, the whole processes still remain elusive. Polycomb group (PcG) proteins are epigenetic chromatin modifiers involved in gene silencing, cancer development and the maintenance of embryonic and adult stem cells. By screening proteins responding to DNA damage using laser micro-irradiation, we found that PHF1, a human homolog of Drosophila polycomb-like, Pcl, protein, was recruited to DSBs immediately after irradiation and dissociated within 10 min. The accumulation at DSBs is Ku70/Ku80-dependent, and knockdown of PHF1 leads to X-ray sensitivity and increases the frequency of homologous recombination in HeLa cell. We found that PHF1 interacts physically with Ku70/Ku80, suggesting that PHF1 promotes nonhomologous end-joining processes. Furthermore, we found that PHF1 interacts with a number of proteins involved in DNA damage responses, RAD50, SMC1, DHX9 and p53, further suggesting that PHF1, besides the function in PcG, is involved in genome maintenance processes.

Mismatch repair (MMR) proteins contribute to genome stability by excising DNA mismatches introduced by DNA polymerase. Although MMR proteins are also known to influence cellular responses to DNA damage, how MMR proteins respond to DNA damage within the cell remains unknown. Here, we show that MMR proteins are recruited immediately to the sites of various types of DNA damage in human cells. MMR proteins are recruited to single-strand breaks in a poly(ADP-ribose)-dependent manner as well as to double-strand breaks. Using mutant cells, RNA interference and expression of fluorescence-tagged proteins, we show that accumulation of MutSbeta at the DNA damage site is solely dependent on the PCNA-binding domain of MSH3, and that of MutSalpha depends on a region near the PCNA-binding domain of MSH6. MSH2 is recruited to the DNA damage site through interactions with either MSH3 or MSH6, and is required for recruitment of MLH1 to the damage site. We found, furthermore, that MutSbeta is also recruited to UV-irradiated sites in nucleotide-excision-repair- and PCNA-dependent manners. Thus, MMR and its proteins function not only in replication but also in DNA repair.