HIV1 Tat Specific Factor 1 (HTATSF1), also known as elongin A2, is a cellular protein initially identified for its role in regulating HIV-1 transcription. It interacts with the viral Tat protein to enhance transactivation of HIV-1 long terminal repeats (LTRs), promoting viral RNA elongation. Beyond viral processes, HTATSF1 functions in cellular transcription, associating with RNA polymerase II to facilitate transcriptional elongation and pre-mRNA splicing. It is ubiquitously expressed, with roles in cell cycle progression and stress responses. Dysregulation of HTATSF1 may contribute to viral pathogenesis and certain cancers, making it a target for studying host-virus interactions and therapeutic development.Besides,Serine/Arginine Rich Splicing Factor 2 (SRSF2) has been identified as an interactor of HTATSF1, thus a functional binding ELISA assay was conducted to detect the interaction of recombinant mouse HTATSF1 and recombinant human SRSF2. Briefly, HTATSF1 was diluted serially in PBS with 0.01% BSA (pH 7.4). Duplicate samples of 100 μl were then transferred to SRSF2-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST and incubated for 1h with anti-HTATSF1 pAb, then aspirated and washed 3 times. After incubation with HRP labelled secondary antibody for 1h at 37℃, wells were aspirated and washed 5 times. With the addition of substrate solution, wells were incubated 15-25 minutes at 37℃. Finally, add 50 µL stop solution to the wells and read at 450/630nm immediately. The binding activity of recombinant mouse HTATSF1 and recombinant human SRSF2 was shown in Figure 1, the EC50 for this effect is 0.466 µg/mL.