AlphaB-Crystallin has for a long time been considered a specific eye lens protein. Later on it appeared that this protein belongs to the family of the small heat shock proteins and that it occurs also extra-lenticularly in many different cell types. AlphaB-Crystallin is mainly present in the cytoplasm, but there are some indications that it might have a function in the nucleus too. However, till now its presence in the nucleus is uncertain. We therefore compared the localization of alphaB-crystallin in nine cell lines cultured under normal conditions using four different antisera. All four antisera gave a diffuse staining for alphaB-crystallin in the cytoplasm, but one of the antibodies consistently showed nuclear staining in eight of the cell types, in the form of distinct speckles. These speckles are equally pronounced in the different cell types, whether or not cytoplasmic alphaB-crystallin is present. Preabsorption of the antiserum with alphaB-crystallin abolished the staining. Furthermore we demonstrate that if only minor amounts of alphaB-crystallin are present, the protein seems to be located exclusively in the nucleus. However, in case of higher amounts of protein, alphaB-crystallin is distributed between cytoplasm and nucleus. The nuclear alphaB-crystallin exists, like the cytoplasmic alphaB-crystallin, in non-phosphorylated and phosphorylated forms, is Triton-insoluble but can be extracted by 2 M NaCl. These data suggest that alphaB-crystallin might be bound to the nuclear matrix per se or to nuclear matrix proteins via other proteins. In agreement with other nuclear matrix proteins, nuclear alphaB-crystallin staining turns diffuse upon mitosis and leaves the chromosomes unstained. Double staining experiments revealed colocalization of alphaB-crystallin with the splicing factor SC35 in nuclear speckles, suggesting a role for alphaB-crystallin in splicing or protection of the splicing machinery.

中文翻译：

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小热激蛋白αB-晶状体蛋白的核染色与剪接因子SC35共定位。

长期以来，AlphaB-Crystallin被认为是一种特殊的眼镜镜片蛋白。后来发现该蛋白属于小热激蛋白家族，在许多不同的细胞类型中也都在镜外出现。AlphaB-晶体蛋白主要存在于细胞质中，但有迹象表明它也可能在细胞核中起作用。但是，到目前为止，它在核中的存在还不确定。因此，我们比较了正常条件下使用四种不同抗血清培养的9种细胞系中alphaB-crystallin的定位。所有四种抗血清在细胞质中均对αB-晶状体蛋白进行了弥漫性染色，但是其中一种抗体在八种细胞类型中始终显示出呈斑点状的核染色。无论是否存在细胞质αB-晶状体蛋白，在不同的细胞类型中这些斑点同样明显。用αB-结晶蛋白预吸收抗血清消除了染色。此外，我们证明，如果仅存在少量的alphaB-crystallin，则该蛋白质似乎仅位于细胞核中。但是，在蛋白质含量较高的情况下，αB-晶状体蛋白分布在细胞质和细胞核之间。核αB-晶状蛋白与细胞质αB-晶状蛋白一样，以非磷酸化和磷酸化形式存在，不溶于Triton，但可用2 M NaCl萃取。这些数据表明，αB-晶状体蛋白可能与核基质本身结合，或通过其他蛋白质与核基质蛋白结合。与其他核基质蛋白一致，核αB-晶状体蛋白染色在有丝分裂时会扩散，使染色体未染色。双重染色实验揭示了αB-晶状蛋白与剪接因子SC35在核斑点中的共定位，表明αB-晶状蛋白在剪接或保护剪接机制中的作用。