Xeroderma pigmentosum group D (XPD) protein is one of the subunits of TFIIH that is required for nucleotide excision repair and transcription. We found a XPD protein complex containing MMS19 that was assumed to be a regulator of TFIIH. However, the MMS19-XPD complex did not contain any other subunits of TFIIH. Instead, it included FAM96B (now designated MIP18), Ciao1, and ANT2. MMS19, MIP18, and XPD localized to the mitotic spindle during mitosis. The siRNA-mediated knockdown of MMS19, MIP18, or XPD led to improper chromosome segregation and the accumulation of nuclei with abnormal shapes. In addition, the frequency of abnormal mitosis and nuclei was increased in XP-D and XP-D/CS patients' cells. These results indicate that the MMS19-XPD protein complex, now designated MMXD (MMS19-MIP18-XPD), is required for proper chromosome segregation, an abnormality of which could contribute to the pathogenesis in some cases of XP-D and XP-D/CS.

Inner nuclear membrane proteins interact with chromosomes in the nucleus and are important for chromosome activity. Lem2 and Man1 are conserved members of the LEM-domain nuclear membrane protein family. Mutations of LEM-domain proteins are associated with laminopathy, but their cellular functions remain unclear. Here, we report that Lem2 maintains genome stability in the fission yeast Schizosaccharomyces pombe. S. pombe cells disrupted for the lem2 + gene (lem2Δ) showed slow growth and increased rate of the minichromosome loss. These phenotypes were prominent in the rich culture medium, but not in the minimum medium. Centromeric heterochromatin formation was augmented upon transfer to the rich medium in wild-type cells. This augmentation of heterochromatin formation was impaired in lem2Δ cells. Notably, lem2Δ cells occasionally exhibited spontaneous duplication of genome sequences flanked by the long-terminal repeats of retrotransposons. The resulting duplication of the lnp1 + gene, which encodes an endoplasmic reticulum membrane protein, suppressed lem2Δ phenotypes, whereas the lem2Δ lnp1Δ double mutant showed a severe growth defect. A combination of mutations in Lem2 and Bqt4, which encodes a nuclear membrane protein that anchors telomeres to the nuclear membrane, caused synthetic lethality. These genetic interactions imply that Lem2 cooperates with the nuclear membrane protein network to regulate genome stability.

Although it is important to remember that this study was not a prospective randomized trial and, thus, had from certain biases, we believe that if a tumor is more than 5 cm. and/or the surgeon is not yet skilled in laparoscopic adrenalectomy, the lateral transperitoneal approach is the most suitable method. If the surgeon has performed at least 20 operations, the adrenal tumor is unilateral and the lesion is less than 5 cm., the lateral retroperitoneal approach seems to be more suitable because of its minimally invasive nature. The lateral retroperitoneal approach is also preferred in patients with a history of upper abdominal surgery. With improvements in technique and new instruments the time required for the lateral retroperitoneal approach has been significantly decreased.

Background: LBR is an inner nuclear membrane protein that participates in heterochromatin organization. Results: LBR recognizes specific histone modifications and induces chromatin compaction and transcriptional repression. Conclusion: LBR tethers epigenetically marked chromatin to the NE to repress transcription. Significance: This finding provides an implication of how transcriptional activities are repressed beneath the NE.

Emerin is the gene product of STA whose mutations cause Emery-Dreifuss muscular dystrophy. It is an inner nuclear membrane protein and phosphorylated in a cell cycle-dependent manner. However, the means of phosphorylation of emerin are poorly understood. We investigated the regulation mechanism for the binding of emerin to chromatin, focusing on its cell cycle-dependent phosphorylation in a Xenopus egg cell-free system. It was shown that emerin dissociates from chromatin depending on mitotic phosphorylation of the former, and this plays a critical role in the dissociation of emerin from barrier-to-autointegration factor (BAF). Then, we analyzed the mitotic phosphorylation sites of emerin. Emerin was strongly phosphorylated in an M-phase Xenopus egg cell-free system, and five phosphorylated sites, Ser 49 , Ser 66 , Thr 67 , Ser 120 , and Ser 175 , were identified on analysis of chymotryptic and tryptic emerin peptides using a phosphopeptide-concentrating system coupled with a Titansphere column, which specifically binds phosphopeptides, and tandem mass spectrometry sequencing. An in vitro binding assay involving an emerin S175A point mutant protein suggested that phosphorylation at Ser 175 regulates the dissociation of emerin from BAF. The nuclear envelope (NE)2 is a highly dynamic structure that disassembles at the onset of mitosis and reassembles on the surface of chromatin during telophase in vertebrates. These changes of NE are crucial for cell cycle progression. The NE consists of an outer nuclear membrane, inner nuclear membrane, nuclear pore complex, and nuclear lamina. The inner nuclear membrane contains integral membrane proteins, i.e. lamin B receptor (LBR), lamina-associated polypeptide-2␤ (LAP2␤), emerin, MAN1, and others, which interact with DNA and/or chromatin, and these proteins are proposed to participate in nuclear membrane targeting to chromatin at an early stage of nuclear assembly (1). The interactions between some of the inner nuclear membrane proteins and chromatin are regulated through phosphorylation of these inner nuclear membrane proteins. The phosphorylation mechanisms for LBR and LAP2␣ and 2␤ are well understood (2-7). LBR directly binds to DNA in vitro and dissociates on phosphorylation by cdc2 kinase and other kinase(s) in a mitotic egg extract (3). LAP2␤ binds to lamin B1 and chromatin, and cell cycle-dependent phosphorylation of LAP2␤ cancels this binding (4). Phosphorylation of these inner nuclear proteins, therefore, is likely to be one of the key mechanisms that control the interactions between the inner nuclear proteins and components of the nuclear lamina as well as chromatin. In this study, we focused on the mitotic phosphorylation of emerin, one of the inner nuclear membrane proteins.Human emerin is a serine-rich protein exhibiting an apparent mass of 34 kDa on SDS-PAGE (8) and is phosphorylated in a cell cycle-dependent manner (9). Emerin belongs to the LEM (LAP2␤, emerin, MAN1) protein family, whose members have approximately a 40-residue domain named the LEM (10). These ...