DNA-PKcs plays a dominant role in the regulation of H2AX phosphorylation in response to DNA damage and cell cycle progression.

Background: When DNA double-strand breaks (DSB) are induced by ionizing radiation (IR) in cells, histone H2AX is quickly phosphorylated into gamma-H2AX (p-S139) around the DSB site. The necessity of DNA-PKcs in regulating the phosphorylation of H2AX in response to DNA damage and cell cycle progression was investigated.

Results: The level of gamma H2AX in HeLa cells increased rapidly with a peak level at 0.

Overexpression of the LKB1 gene inhibits lung carcinoma cell proliferation partly through degradation of c-myc protein.

LKB1 encodes a serine/threonine kinase generally inactivated in human lung cancers, which mediates cancer cell proliferation, migration and differentiation, but its biological function has not been completely elucidated. In this study, we demonstrated that LKB1 was associated with a substantial reduction of c-myc expression by using an inducible LKB1 expression system in the LKB1-null lung cell line A549. Nevertheless, the reduction of the c-Myc gene expression was not accompanied by corresponding reduction of mRNAs but protein, which can be abrogated by a proteosome inhibitor (MG132), suggesting that the reduction was associated with their increased degradation rather than transcriptional controls.

[The relationship between test anxiety and personality, self-esteem in grade one senior high students].

Objective: To explore the relationship between test anxiety and personality, self-esteem in grade one senior high school students.

Methods: Totally 538 senior high school students of grade one were investigated by Test Anxiety Scale (TAS), Eysenck Personality Questionnaire (EPQ) and Self-Esteem Scale (SES) in a Senior High School in Shandong Province.

Results: The prevalence of test anxiety among all the surveyed students was rated 65.

Downregulation of c-myc protein by siRNA-mediated silencing of DNA-PKcs in HeLa cells.

DNA-dependent protein kinase (DNA-PK) has been intensively investigated for its roles in the nonhomologous end-joining (NHEJ) pathway of DNA double-strand break repair and maintenance of genomic stability. Its catalytic subunit, DNA-PKcs, a serine/threonine protein kinase, has recently been reported to be overexpressed in various human cancers, but its significance is unclear. In our study, we synthesized 3 small interfering RNA (siRNA) oligonucleotides, which separately target the translation initiation region, catalytic motif and a sequence between the scid-mutation region and the FATC motif of DNA-PKcs; 3 stable cell lines were generated from HeLa cells transfected with these siRNA constructs, respectively.