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Proliferating cell nuclear antigen (PCNA) is a 28kDa nuclear protein associated with the cell cycle, a nuclear protein vital for cellular DNA synthesis. Proliferating cell nuclear antigen was originally identified by immunofluorescence as a nuclear protein whose appearance correlated with the proliferate state of the cell. PCNA is required for replication of DNA in vitro and has been identified as the auxiliary protein (cofactor) for DNA polymerase delta. The anti-PCNA antibodies react with th

The cyclophilins are a conserved class of proteins that bind the immunosuppressive drug cyclosporin A (CsA) with high affinity. CsA blocks helper T-cell activation at a step between T-cell receptor stimulation and the transcriptional activation of cytokine genes. Cyclophilins from many species possess peptidyl-prolyl cis-trans isomerase (PPIase) activity that is blocked by CsA and therefore may be relevant in CsA-mediated immunosuppression.

Modulation of the chromatin structure plays an important role in the regulation of transcription in eukaryotes. The nucleosome, made up of four core histone proteins (H2A, H2B, H3 and H4), is the primary building block of chromatin. The N-terminal tail of core histones undergoes different posttranslational modifications including acetylation, phosphorylation and methylation. These modifications occur in response to cell signal stimuli and have a direct effect on gene expression. In most spec