Fleisig Helen B, Liang Hong, Nagarajan Lalitha
Department of Molecular Genetics, M,D, Anderson Cancer Center, 1515 Holcombe Blvd,, Houston TX 77030, USA.
J Mol Signal. 2010 Jun 11;5:6. doi: 10.1186/1750-2187-5-6.
Transient expression of adenoviral oncoprotein E1B55K in normal cells induces aggresome formation and sequestration of critical host proteins in aggresomes. Our previous studies reported that Sequence Specific Binding Protein 2 (SSBP2), a candidate tumor suppressor is recruited to aggresomes in adenovirally transformed human embryonal kidney 293 (HEK293) cells. To understand the extent and significance of the E1B55K-SSBP2 interactions in these cells, we have examined SSBP2 localization under conditions of stress in HEK293 cells. SSBP2 localizes to PML- Nuclear Bodies (PML-NBs) in response to inhibition of nuclear export, treatment with etoposide, hydroxyurea or gamma irradiation only in HEK293 cells. Furthermore, the PML-NBs grow in size and number in response to radiation over a 24 hour period in HEK293 cells analogous to previous findings for other cell types. Nonetheless, we conclude that E1B55K subverts SSBP2 function in HEK293 cells. These findings demonstrate the limitations in using HEK293 cells to study DNA damage response and other cellular processes since SSBP2 and similar regulatory proteins are aberrantly localized due to constitutive E1B55K expression.
腺病毒癌蛋白E1B55K在正常细胞中的瞬时表达会诱导聚集体形成，并将关键宿主蛋白隔离在聚集体中。我们之前的研究报道，候选肿瘤抑制因子序列特异性结合蛋白2（SSBP2）在腺病毒转化的人胚肾293（HEK293）细胞中被募集到聚集体中。为了了解这些细胞中E1B55K与SSBP2相互作用的程度和意义，我们检测了HEK293细胞在应激条件下SSBP2的定位。仅在HEK293细胞中，SSBP2会因核输出抑制、用依托泊苷、羟基脲处理或γ射线照射而定位到早幼粒细胞白血病核小体（PML-NBs）。此外，与之前其他细胞类型的研究结果类似，在HEK293细胞中，PML-NBs在24小时内会因辐射而增大尺寸并增加数量。尽管如此，我们得出结论，E1B55K在HEK293细胞中破坏了SSBP2的功能。这些发现表明，由于组成型E1B55K表达导致SSBP2和类似调节蛋白定位异常，使用HEK293细胞研究DNA损伤反应和其他细胞过程存在局限性。
