Regulated expression of TATA-binding protein-related factor 3 (TRF3) during early embryogenesis.

RNA polymerase (Pol) II transcription persists in TATA-box-binding protein (TBP)(-/-) mutant mouse embryos, indicating TBP-independent mechanisms for Pol II transcription in early development. TBP-related factor 3 (TRF3) has been proposed to substitute for TBP in TBP(-/-) mouse embryos. We examined the expression of TRF3 in maturing oocytes and early embryos and found that TRF3 was co-expressed with TBP in the meiotic oocytes and early embryos from the late one-cell stage onward. The amounts of TBP and TRF3 changed dynamically and correlated well with transcriptional activity. Chromatin immunoprecipitation (ChIP) assay revealed that different gene promoters in mouse embryonic stem (ES) cells recruited TRF3 and TBP selectively. Comparative analyses of TRF3 and TBP during cell cycle showed that both factors proceeded through cell cycle in a similar pace, except that TRF3 was slightly delayed than TBP in entering the nucleus when cells were exiting the M-phase. Data from expression and biochemical analyses therefore support the hypothesis that TRF3 plays a role in early mouse development. In addition, results from co-localization study suggest that TRF3 may be also involved in Pol I transcription.