Localization and differential expression of the Krüppel-associated box zinc finger proteins 1 and 54 in early mouse development.

Upon fertilization, the zygotic genome is activated. To ensure the transcription of specific genes and avoid promiscuous gene expression, a chromatin-mediated repressive state is established. To characterize potential heterochromatin factors present during the first cleavage, two putative transcriptional repressors, zinc finger protein (ZFP1) and ZFP54, belonging to the Krüppel-associated box (KRAB) zinc finger family, were isolated. ZFP1 and ZFP54 contain an N-terminally located KRAB repressor domain followed by 8 and 12 repeats of Krüppel zinc-finger motifs, respectively. Reverse transcription (RT) and quantitative (q) PCR show that maternally contributed Zfp1 and Zfp54 mRNA are detected throughout preimplantation development. α-Amanitin-treated zygotes revealed that maternal Zfp1 and Zfp54 are fully degraded at the two-cell stage. Microinjections of in vitro-transcribed mRNA encoding a gfp-fused reporter gene into zygotes demonstrated the intracellular distribution of ZFP1-green fluorescent protein (GFP) and ZFP54-GFP colocalized with a DNA marker in the two-cell embryo. The KRAB domain was essential to colocalize with DNA, and deletion of the KRAB domain in ZFP1-GFP and ZFP54-GFP localized in nucleoli and in a ubiquitously manner, respectively. Taken together, this suggests a role for ZFP1 and ZFP54 in transcriptional regulation in early development.