The Functional Studies Of Heterochromatin Protein HP1α And LaminA

HP1(Heterochromatin protein1) is a nonhistone chromosomal protein because of its association with heterochromatin. Numerous studies have shown that such a protein plays a role in gene activity and silencing, telomere capping and silencing, tumorigenesis. There are still many unknown functions of HP1.People have been focusing on the studies between heterochromatin and HP1.We mainly studied the biological functions of HP1α in the lower structure of chromatin that are three levels:histone, DNA-histone complex, nucleosome.We mainly used many technologies:GST-HP1α pulldown assay, the cross-linking assay by cross-linker BS3, the Western blot assay, the biotin labeled DNA assay and the electrophoretic mobility shift assay. We observed that HP1α maybe play a role of chaperon which helps H2A-H2B dimmer to assemble into H3-H4-DNA complex, or HPl a maintain the stability of nucleosome. The interactions between HP1α and histone variants have different strength, such as the interactions between HP la and H2A.Z-H2B dimmer is stronger than that between HP1α and H2A-H2B dimmer. HP1α could promote the assembly of H2A nucleosome, but it could not promote the assembly of H2A.Z nucleosome. The binding abilities of HP1were not significant influence on H3.3varient Compared with H3.1. To sum up, HPla maybe played a role of chaperon which helps the assembly of nucleosome, the mechanism was complex and we need further exploration.In cell nucleus, heterochromatin is anchored nuclear membrane by the interaction between Lamin protein and DNA. Lamin is located underneath the inner nuclear membrane(INM). Hutchinson-Gilford progeria syndrome (HGPS) is caused by the mutations in LMNA. The majority of HGPS cases are associated with a splicing defect in exon resulting in the LaminA lacking50amino acides and the change of posttranslational modifications. The formation of the truncated protein is named progeria. Telomeres DNA and human ageing is closely related, the telomere3’overhang are G rich sequences,can form hairpins that dimerize to give rise to G-quadruplex DNA structure(G4). G4structure inhibit the recruitment of telomerase, resulting in inhibiting telomere elongation and inhibiting cancer. According to our previous research, G4and LaminA were closely related with aging. But whether is a relationship between LaminA and G4? So far, nobody know it. this is the purpose of the study.We mainly used many technologies:the circular dichroism spectrometer (CD) assay, the electrophoretic mobility shift assay, the AlphaScreen assay. Our study found that LaminA could bind G4structure specially. When telomere DNA sequences were disturbed, G4structure were not formed, and the interactions between LaminA and disturbed sequences were weakly. While RHPS4changed G4structure, the interactions between LaminA and G4had been inhibited. Taken together, these results will shed light on the molecular mechanism underlying LaminA/G4associated HPGS and cancer.