Conclusion The present study showed that Tax arrested cells at Compound C the G1 phase of the cell cycle, thereby inducing apoptosis. Taken together, the results demonstrate that Tax exerts a significant impact on cellular factors that regulate the cell cycle and the induction of apoptosis. Importantly, to the best of our knowledge, this is the first study to high light the morphological dynamics of Tax induced cell death after cell cycle arrest at the G1 phase. This overview can be extended to Tax mediated sig naling, and further study of the interactions between Tax and cellular factors will provide insights into the mechanisms by which Tax regulates host cell behavior, as well as the mechanisms underlying lymphoma induc tion and progression induced by HTLV 1.

Methods Cell lines and transfections Human cervical HeLa cells and Fucci2 expressing HeLa cells were maintained in Dulbeccos modified Eagles medium supple mented with 10% heat inactivated fetal bovine serum and 100 units ml penicillin streptomycin. Cells were transiently transfected with a Tax expression vector, or a control vector, using Fugene HD according to the manufacturers instructions. The underlined sequences correspond to restriction enzyme sites specific for XhoI and NotI, respectively. A Flag sequence was included at the 3 end of the tax gene. Full length tax was then cloned into the XhoI and NotI restriction sites in the pCAGGS mammalian expression vector. To generate the pCAGGS Tax IRES CFP vector and the pCAGGS IRES CFP control vector, the IRES was amplified from the pRetroX IRES ZsGreen1 vector and CFP was amplified from the pCS2 vector.

The IRES and CFP sequences were then inserted into the pCAGGS con trol vector or a pCAGGS vector containing Flag tagged Tax. The vector pEGFP N1 encodes a red shifted variant of wild type GFP that was modified for brighter fluorescence and which was used as a reporter to identify trans fected cells by flow cytometry. The pSV B galactosidase vector encoding a bacterial B galactosidase and pRL SV40 encoding Renilla luciferase were used to normalize the transfection efficiency. pGV HL21 encodes five tandemly repeated 21 bp enhancers of HTLV 1, each of which contain a CRE motif and pGV and have been previously decribed. RNA extraction HeLa cells were transiently transfected with Tax or the control vector and incubated for 30 h.

RNA from AV-951 total cell extracts was isolated using the RNeasy Mini Kit according to the manufacturers instructions. RNA was quantified using a spectrophotometer and stored at ?80 C. For gene chip analysis, the quality of RNA was determined using the Agilent Bioanalyzer. Microarray analysis RNA samples were analyzed by microarray using the GeneChip Human Genome U133A 2. 0 Array. Microarray hybridization and fluorescence detection were performed as described in the Affymetrix Gene Chip Expression Analysis Technical Manual.