ABSTRACT
Molecules can enter the nucleus by passive diffusion or active transport mechanisms, depending on their size. Small molecules up to size of 50-60 kDa or less than 10 nm in diameter can diffuse passively through the nuclear pore complex (NPC), while most proteins are transported by energy driven transport mechanisms. Active transport of viral proteins is mediated by nuclear localization signals (NLS), which were first identified in Simian Virus 40 large T antigen and had subsequently been identified in a large number of viral proteins. Usually they contain short stretches of lysine or arginine residues. These signals are recognized by the importin super-family (importin α and β) proteins that mediate the transport across the nuclear envelope through Ran-GTP. In contrast, only one class of the leucine-rich nuclear export signal (NES) on viral proteins is known at present. Chromosome region maintenance 1 (CRM1) protein mediates nuclear export of hundreds of viral proteins through the recognition of the leucine-rich NES.
ABSTRACT
As one of the immediate-early(IE)proteins of herpes simplex virus type 1(HSV-1),ICP22 is a multifunctional viral regulator that localizes in the nucleus of infected cells.It is required in experimental animal systems and some nonhuman cell lines,but not in Vero or HEp-2 cells.ICP22 is extensively phosphorylated by viral and cellular kinases and nucleotidylylated by casein kinase Ⅱ.It has been shown to be required for efficient expression of early(E)genes and a subset of late(L)genes.ICP22,in conjunction with the UL13 kinase,mediates the phosphorylation of RNA polymerase Ⅱ.Both ICP22 and UL13 are required for the activation of ode2,the degradation of cyclins A and B and the acquisition of a new cdc2 partner,the UL42 DNA polymerase processivity factor.The cdc2-UL42 complex mediates postranscriptional modification of topoisomerase Ⅱa in an ICP22-dependent manner to promote L gene expression.In addition,ICP22 interacts with cdk9 in a Us3 kinase dependent fashion to phosphorylate RNA polymerase Ⅱ.
ABSTRACT
Herpes simplex virus type 1 (HSV-1) is the causative agent of cold sores and other more serious diseases. HSV-1 infected-cell protein 27 (ICP27) is an immediate-early regulatory phosphoprotein homologous to gene products identified in all classes of herpesviruses so far. To raise the antiserum to ICP27 for further characterization of its biological function, the ICP27 gene was cloned into the pET-28a (+) vector, then ICP27 protein was expressed in E. Coli and purified by nickel-nitrilotriacetic acid (Ni2+-NTA) affinity resin column,finally the purified protein was used to raise antiserum. Western blot analysis demonstrated that the antiserum recognized the recombinant protein, and the antiserum was able to probe the ICP27 in HSV-1 infected cells with high specificity by immunofluorescence assay (IFA). Therefore, the specific antiserum will provide a valuable tool for further studies investigating ICP27's biological function during HSV-1 infection.