Chang C C, Zhang J, Lombardi L, Neri A, Dalla-Favera R
Department of Pathology, College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA.
Mol Cell Biol. 1995 Sep;15(9):5180-7. doi: 10.1128/MCB.15.9.5180.
The NFKB-2 gene codes for an NF-kappa B-related transcription factor containing rel-polyG-ankyrin domains. Chromosomal rearrangements of the NFKB-2 locus have been found in various types of lymphoid neoplasms, suggesting that they may contribute to lymphomagenesis. Rearrangements cluster within the 3'-terminal ankyrin-encoding domain of the NFKB-2 gene and lead to the production of C-terminally truncated proteins which, in some cases, are fused to heterologous protein domains. In order to determine the functional consequences of these alterations, we have analyzed the subcellular localization, DNA binding, and transcriptional activity of two representative tumor-associated mutants in which the ankyrin domain is either terminally truncated (NFKB-2p85) or truncated and joined to an out-of-frame immunoglobulin C alpha domain (lyt-10C alpha). Immunofluorescence studies performed on cells transfected with p85 or lyt-10C alpha expression vectors showed that both the abnormal proteins were constitutively localized in the nucleus. Immunoprecipitation analysis of UV-cross-linked DNA-protein adducts showed that p85 can bind kappa B sites in its unprocessed form. Cotransfection of p85 or lyt-10C alpha expression vectors with kappa B-driven reporter plasmids showed that both p85 and lyt-10C alpha have retained the ability to mediate transcriptional activation via heterodimerization with Rel-Ap65 but have lost the transrepression activity associated with homodimeric DNA binding. Furthermore, both p85 and lyt-10C alpha were capable of independent transactivation of kappa B-reporter genes and this activity could not be further stimulated by Bcl-3. These abnormal proteins may contribute to lumphomagenesis by determining a constitutive activation of the NF-kappa B system and, in particular, of NFKB-2 target genes.
NFKB - 2基因编码一种包含rel - 多聚G - 锚蛋白结构域的NF - κB相关转录因子。在各种类型的淋巴瘤中发现了NFKB - 2基因座的染色体重排，这表明它们可能参与淋巴瘤的发生。重排聚集在NFKB - 2基因的3'末端锚蛋白编码结构域内，并导致产生C末端截短的蛋白质，在某些情况下，这些蛋白质与异源蛋白结构域融合。为了确定这些改变的功能后果，我们分析了两种代表性的肿瘤相关突变体的亚细胞定位、DNA结合和转录活性，其中锚蛋白结构域要么在末端截短（NFKB - 2p85），要么截短并与框外免疫球蛋白Cα结构域连接（lyt - 10Cα）。对用p85或lyt - 10Cα表达载体转染的细胞进行的免疫荧光研究表明，这两种异常蛋白都组成性地定位于细胞核中。对紫外线交联的DNA - 蛋白质加合物的免疫沉淀分析表明，p85可以以未加工的形式结合κB位点。用κB驱动的报告质粒与p85或lyt - 10Cα表达载体共转染表明，p85和lyt - 10Cα都保留了通过与Rel - Ap65异源二聚化介导转录激活的能力，但失去了与同型二聚体DNA结合相关的反式抑制活性。此外，p85和lyt - 10Cα都能够独立激活κB报告基因，并且这种活性不能被Bcl - 3进一步刺激。这些异常蛋白可能通过确定NF - κB系统，特别是NFKB - 2靶基因的组成性激活而参与淋巴瘤的发生。
