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F. Zhuang, J. Zhao, Y.-H. Liu; Expression and Function of Eaf2. Invest. Ophthalmol. Vis. Sci. 2008;49(13):1717.
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Microphthalmia/anophthalmia is a relatively common genetic malformation that causes vision impairment and blindness with a birth prevalence ranging from 1 to 2 per 10,000. Any disruption to the early inductive phase or subsequent proliferation and differentiation phase of eye development will lead to anophthalmia/ microphthalmia. To fully understand its underlying causes, we need to first identify key molecular players and their mechanisms of actions. The purpose of the current investigation is to functionally characterize Eaf2, a new addition to a growing list of nuclear factors that are involved in ocular development and function.
In situ hybridization was used to determine the temporal and spatial pattern of Eaf2 gene expression. Cell transfection experiments were performed to initially characterize its possible functional activities in transcriptional regulation, cell cycle control and in response to stress stimuli. Deletion analysis was used to define functional domains.
Eaf2 has been reported to show transcription activation properties through its association with ELL to enhance its RNA polymerase II elongation activity. In this study, we showed that Eaf2 is highly expressed in the differentiated lens fiber cells and retinal neurons during ocular development. To demonstrate its dynamic sub-cellular activities, we utilized GFP-EAF2 fusion protein and followed its expression in transfected cells. GFP-EAF2 is preferentially localized to the nucleus, and in the presence of ELL, it accumulates in nuclear speckles. However, Eaf2 is a highly unstable nuclear protein as the nuclear localization is a transient phenomenon with a protein half-life of approximately 24 hours. In long term culture, Eaf2 is present at minute quantities in the cytoplasm but is excluded from the nucleus. Furthermore, we provide evidence that nuclear distribution of Eaf2 is responsive to DNA damage stimulation, as following UV irradiation, EAF2 is relocated to nucleoli, suggesting a possible functional involvement in DNA damage repair.
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