Manjinder Nanrey 12855110Recruitment of proteins such as TAT ​​and P-TEFb is required to free RNAPII from pausing at the promoter-proximal hairpin loop. Currently supported, but oversimplified, models tell us that Tat binds to the hairpin loop created by the Tar sequence of the HIV LTR, which then recruits P-TEFb. Through the use of CDK9, p-TEFb then phosphorylates Ser2 of the CTD and allows elongation. However, another protein called TCERG1 has been found to be involved in the phosphorylation of Ser 2. This protein, originally called CA150 (2), has been characterized in the past, but no appropriate model describing how TCERG1 functions in vivo was available. regarding HIV-1 transcriptional elongation. In our current article we evaluated the role of TCERG1 and hypothesized that TCERG1 is a cofactor for HIV transcriptional elongation. We examined the effects of TCERG1 knockdown by shRNA in PBL and Jerkat cells transfected with the HIV-1 LTR with the Luciferase reporter fused to the env gene and found that both basal and Tat-activated transcription were decreased . This suggested that TCERG1 served as a positive regulator of transcription. To test the effect of TCERG1 on elongation we measured the amount of transcription in distal regions of the LTR in HEK293T cells with a reverse transcriptase deletion of the transiently transfected HIV-1 plasmid. We found that knocking down TCERG1 reduced transcript production by 30–40%. To directly measure the rate of transcription we measured the level of transcription using 2 lines, one of which did not contain the shRNA for TCERG1 (control). We treated both cell lines with DRM, which blocks gene transcription in vivo, and measured the recovery of distal transcription… middle of paper… pinches and assembles transcription and splicing components into complexes across its amino acids and carboxyl regions." Molecular and Cellular Biology 26.13 (2006): 4998-5014. Molecular and Cellular Biology. Web. .(4,7) Kodama, Yutaka, and Chang-Deng Hu. "Bimolecular Fluorescence Complementation (BiFC): A Five-year update and future prospects." BioTechniques 53.5 (2012): 285-98. BioTechniques. Web. .(8) Shilatifard, Ali, et al. "Ell2, a New Member of an Ell Family of Rna Polymerase Ii Elongation Factors." Proceedings of the National Academy of Sciences 94.8 (1997): 3639-43. Print.(5,6) Gaj, T., C. A. Gersbach, and C. F. Barbas. “Zfn-, Talen-, and Crispr/Cas-Based Methods for Genome Engineering. " Trends Biotechnol 31.7 (2013): 397-405. Print.