Elongator complex has been associated with hyperphosphorylated RNA polymerase II and is known to play critical roles in transcriptional elongation, as well as in tRNA modification and exocytosis. However, the specific mechanism of how human Elongator complex regulates cell growth and cell cycle remains unclear. To investigate the composition of human Elongator complex and its effects on cell growth, 293T cells were established that stably overexpressed Flag-Elp3 and Flag-Elp4. By using anti-Flag M2 antibody-bound resin, a core Elongator complex was purified from cells that stably overexpressed Flag-Elp3. No Elongator complex was purified from cells stably transfected with pFlagCMV4-Elp4. Interestingly, the cell growth was inhibited in 293T cells transfected with pFlagCMV4- Elp3. Flow cytometry analysis showed that most of the cells stably overexpressing Flag-Elp3 were found in G1 stage, indicating a role of the core Elongator in the G1 checkpoint for the regulation of cell cycle. We observed increased basal transcription and remarkably enhanced transcription stimulated by VP16 in 293T cells overexpressing Flag-Elp3. The transcription could also be synergistically activated by overexpressing both Elp3 and Elp4. Taken together, our results suggested that the core Elongator complex formed by Elp1, Elp2, and Elp3 was rather stable, whereas Elp4, Elp5, and Elp6 might loosely contact and work together with the core Elongator to regulate cell functions.