Adducin family proteins possess different nuclear export potential

• Main Authors: Chia-Mei Liu, 劉佳玫
• Other Authors: Hong-Chen Chen
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/62275174557953372222

碩士 === 國立中興大學 === 生命科學系所 === 105 === Adducin （ADD） proteins are actin binding proteins mainly localized at actin-spectrin junctions. The ADD family comprises three closely related genes（α, β and γ）. All ADD proteins are similar in their amino acid sequences and domain structures which consist of an amino-terminal head domain, a neck domain, and a carboxyl-terminal protease-sensitive tail domain within which a highly conserved bipartite nuclear localization signal（NLS）is present. Interestingly, only ADD1 has been reported to localize in the nucleus upon loss of cell-cell junctions. In this study, we found that transiently expressed ADD2 and ADD3 distributed only in the cytoplasm, whereas ADD1 distributed both in the cytoplasm and nucleus. However, ADD2 and ADD3 were partially sequestered in the nucleus in the presence of leptomycin, a CRM1 inhibitor, indicating that ADD2 and ADD3 possess functional NLS and actually shuttle between the cytoplasm and nucleus. Our results also suggest that ADD2 and ADD3 may be quickly transported to the cytoplasm upon entering the nucleus. Indeed, we found that ADD2 and ADD3 possess much higher potential than ADD1 to counteract the activity of the NLS derived from Simian virus 40 large T antigen. All ADD proteins appear to contain multiple nuclear export signals（NES）. A leucine-rich motif （377FEALMRMLDWLGYRT391） present in the neck domain was verified to be a functional NES for ADD1, but not for ADD2 and ADD3. To determine the function of ADD in the nucleus, we identify nuclear ADD binding proteins. Coimmunoprecipitation experiments indicated that transcription factor ZNF331 and RNA polymerase II are associated with ADD1.Taken together, our results provide an example to show that different members in the ADD family could have different potential to retain in the nucleus and suggest that ADD proteins may diversify their localization and function during the evolution.