Expression, Activity, and Subcellular Localization of the Yin Yang 1 Transcription Factor in Xenopus Oocytes and Embryos

Kate Eliassen Marley,Danielle Meyer,Christopher Eskiw,Myra Hurt,Nick Ovsenek,Andrew Ficzycz

doi:10.1074/jbc.m011188200

Kate Eliassen Marley, Danielle Meyer + Show 4 more

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https://doi.org/10.1074/jbc.m011188200

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Abstract

Yin Yang 1 (YY1) is a multifunctional transcription factor that acts as an activator, repressor, or initiator of transcription of numerous cellular and viral genes. Previous studies in tissue culture model systems suggest YY1 plays a role in development and differentiation in multiple cell types, but the biological role of YY1 in vertebrate oocytes and embryos is not well understood. Here we analyzed expression, activity, and subcellular localization profiles of YY1 during Xenopus laevis development. Abundant levels of YY1 mRNA and protein were detected in early stage oocytes and in all subsequent stages of oocyte and embryonic development through to swimming larval stages. The DNA binding activity of YY1 was detected only in early oocytes (stages I and II) and in embryos after the midblastula transition (MBT), which suggested that its potential to modulate gene expression may be specifically repressed in the intervening period of development. Experiments to determine transcriptional activity showed that addition of YY1 recognition sites upstream of the thymidine kinase promoter had no stimulatory or repressive effect on basal transcription in oocytes and post-MBT embryos. Although the apparent transcriptional inactivity of YY1 in oocytes could be explained by the absence of DNA binding activity at this stage of development, the lack of transcriptional activity in post-MBT embryos was not expected given the ability of YY1 to bind its recognition elements. Subsequent Western blot and immunocytochemical analyses showed that YY1 is localized in the cytoplasm in oocytes and in cells of developing embryos well past the MBT. These findings suggest a novel mode of YY1 regulation during early development in which the potential transcriptional function of the maternally expressed factor is repressed by cytoplasmic localization.

Highlights

Yin Yang 1 (YY11; previously referred to as FIII, NF-E1, ␦, F-ACT1, CF1, or UCRBP) is a GLI-Kruppel family transcrip
Expression assays showed that YY1 had no effect on transcription from the thymidine kinase (TK) promoter in oocytes, but we found a similar lack of transcriptional activity in post-midblastula transition (MBT) embryos at a point in development when its DNA binding is reactivated
Transcriptional Activity of YY1 in Xenopus Embryos—We examined the transcriptional activity of YY1 using a series of microinjected reporter constructs containing the thymidine kinase (TK) promoter linked to YY1 binding sites

Summary

Introduction

Yin Yang 1 (YY11; previously referred to as FIII, NF-E1, ␦, F-ACT1, CF1, or UCRBP) is a GLI-Kruppel family transcrip-. Tion factor that functions either as a repressor, activator, or initiator of transcription (reviewed in Ref. 1). It is expressed in a wide variety of different cell types and shows a high degree of sequence similarity among divergent organisms [2,3,4,5]. The emerging picture is that the functional diversity of YY1 as an activator, repressor, or initiator of transcription is context-specific and is modulated by interactions with various cellular factors and adaptor proteins. A variety of tissue culture studies have shown that YY1 controls expression of developmentally regulated genes, and so it is thought to play important roles in development and differentiation (reviewed in Ref. 1).

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