Functional Analysis of Nuclear Pore Complex Protein Nup62/p62 Using Monoclonal Antibodies

Nucleoporin 62-Like Protein is Required for the Development of Pharyngeal Arches through Regulation of Wnt/β-Catenin Signaling and Apoptotic Homeostasis in Zebrafish

We have previously observed the predominant expression of nucleoporin 62-like (Nup62l) mRNA in the pharyngeal region of zebrafish, which raises the question whether Nup62l has important implications in governing the morphogenesis of pharyngeal arches (PA) in zebrafish. Herein, we explored the functions of Nup62l in PA development. The disruption of Nup62l with a CRISPR/Cas9-dependent gene knockout approach led to defective PA, which was characterized by a thinned and shortened pharyngeal region and a significant loss of pharyngeal cartilages. During pharyngeal cartilage formation, prechondrogenic condensation and chondrogenic differentiation were disrupted in homozygous nup62l-mutants, while the specification and migration of cranial neural crest cells (CNCCs) were unaffected. Mechanistically, the impaired PA region of nup62l-mutants underwent extensive apoptosis, which was mainly dependent on activation of p53-dependent apoptotic pathway. Moreover, aberrant activation of a series of apoptotic pathways in nup62l-mutants is closely associated with the inactivation of Wnt/β-catenin signaling. Thus, these findings suggest that the regulation of Wnt/β-catenin activity by Nup62l is crucial for PA formation in zebrafish.

Expression of autophagy-related proteins according to androgen receptor and HER-2 status in estrogen receptor-negative breast cancer

PURPOSE

The purpose of this study was to investigate the expression of autophagy-related proteins in relation to androgen receptor (AR) status in estrogen receptor (ER)-negative breast cancers.

METHODS

We extracted 334 ER-negative breast cancer samples to construct tissue microarrays (TMAs), which were immunohistochemically stained for autophagy-related proteins (beclin-1, LC3A, LC3B, p62) and for AR and HER-2.

RESULTS

There were 127 AR-positive cases and 207 AR-negative cases, and 140 HER-2-positive cases and 194 HER-2 negative cases. The AR-negative group was associated with tumoral LC3A expression (P<0.001), while the AR-positive group was associated with tumoral BNIP3 expression (P<0.001). Tumoral LC3A was most highly expressed in the AR-negative and HER-2 negative group, while stromal LC3A showed the highest expression in the AR-negative and HER-2-positive group. Tumoral BNIP3 and stromal BNIP3 were highest in the AR-positive and HER-2-negative group. In the AR-positive and HER-2-negative group, stromal p62 positivity was an independent factor that was statistically significant in its association with shorter disease-free survival (DFS) (Hazard ratio: 10.21, 95% CI: 1.130-92.31, P = 0.039). Shorter DFS was associated with tumoral LC3A positivity (Hazard ratio: 10.28, 95% CI: 2.068-51.19, P = 0.004) in the AR-negative and HER-2-positive group.

CONCLUSION

In ER-negative breast cancers, AR status was associated with expression of different types of autophagy-related proteins. Tumoral LC3A was most highly expressed in AR-negative breast cancers, while tumor BNIP3 was highest in AR-positive breast cancers.

Local nucleosome dynamics facilitate chromatin accessibility in living mammalian cells

Genome information, which is three-dimensionally organized within cells as chromatin, is searched and read by various proteins for diverse cell functions. Although how the protein factors find their targets remains unclear, the dynamic and flexible nature of chromatin is likely crucial. Using a combined approach of fluorescence correlation spectroscopy, single-nucleosome imaging, and Monte Carlo computer simulations, we demonstrate local chromatin dynamics in living mammalian cells. We show that similar to interphase chromatin, dense mitotic chromosomes also have considerable chromatin accessibility. For both interphase and mitotic chromatin, we observed local fluctuation of individual nucleosomes (~50 nm movement/30 ms), which is caused by confined Brownian motion. Inhibition of these local dynamics by crosslinking impaired accessibility in the dense chromatin regions. Our findings show that local nucleosome dynamics drive chromatin accessibility. We propose that this local nucleosome fluctuation is the basis for scanning genome information.

Expression of autophagy-related markers beclin-1, light chain 3A, light chain 3B and p62 according to the molecular subtype of breast cancer

AIMS

To investigate the relationship between the expression of autophagy-related proteins, including beclin-1, light chain (LC) 3A, LC3B, and p62, and prognosis in invasive breast cancer.

METHODS AND RESULTS

We constructed tissue microarrays from the breast cancer cells of 489 patients, and classified molecular subtypes using surrogate immunohistochemical stains. The tumoral expression levels of LC3A and LC3B were highest in triple-negative breast cancer (TNBC) (P < 0.001), whereas these types of tumour had the lowest expression levels of these markers in the stroma (P = 0.005 and P < 0.001, respectively). Cytoplasmic beclin-1 expression was highest in TNBC, but nuclear expression was lowest (P < 0.001). p62 cytoplasmic and nuclear expression were highest in HER2-type tumours (P = 0.001 and P < 0.001, respectively). Tumoral LC3A and LC3B expression were associated with high histological grade (P < 0.001, and P < 0.028, respectively), but nuclear p62 expression was associated with lower histological grade (P = 0.004).

CONCLUSIONS

Autophagy-related markers are differentially expressed according to the molecular subtype of breast cancer. In particular, expression of LC3A, LC3B and beclin-1 was highest in TNBC tumour cells, whereas that of LC3A and LC3B in the tumour stroma was lowest in TNBC.

Rat monoclonal antibody specific for septin 9

The septin family of GTPase proteins has been shown to be important for cell division, cytoskeletal organization, and membrane-remodeling events. Septin 9 (SEPT9) is a member of the septin family (also designated MSF/eseptin/Sint1) and has been implicated in tumorigenesis. The present study reports on the preparation and properties of a monoclonal antibody (MAb) directed against SEPT9. The antibody was produced by hybridization of mouse myeloma cells with lymph node cells from an immunized rat. The MAb 7B5 specifically recognized SEPT9, as evidenced by immunoblotting using a variety of extracts from cultured cells. In immunostaining using MAb 7B5, a filamentous pattern near the plasma membrane was observed. The MAb 7B5 promises to be useful in immunoblotting and immunostaining experiments in various cells and tissues to determine the expression levels of SEPT9, as well as to further the analysis of the biological function of this protein.

The mobile FG nucleoporin Nup98 is a cofactor for Crm1-dependent protein export

Nup98 is a mobile nucleoporin that forms distinct dots in the nucleus, and, although a role for Nup98 in nuclear transport has been suggested, its precise function remains unclear. Here, we show that Nup98 plays an important role in Crm1-mediated nuclear protein export. Nuclear, but not cytoplasmic, dots of EGFP-tagged Nup98 disappeared rapidly after cell treatment with leptomycin B, a specific inhibitor of the nuclear export receptor, Crm1. Mutational analysis demonstrated that Nup98 physically and functionally interacts with Crm1 in a RanGTP-dependent manner through its N-terminal phenylalanine-glycine (FG) repeat region. Moreover, the activity of the Nup98-Crm1 complex was modulated by RanBP3, a known cofactor for Crm1-mediated nuclear export. Finally, cytoplasmic microinjection of anti-Nup98 inhibited the Crm1-dependent nuclear export of proteins, concomitant with the accumulation of anti-Nup98 in the nucleus. These results clearly demonstrate that Nup98 functions as a novel shuttling cofactor for Crm1-mediated nuclear export in conjunction with RanBP3.

Live imaging system for visualizing nuclear pore complex (NPC) formation during interphase in mammalian cells

Nuclear pore complexes (NPCs) are 'supramolecular complexes' on the nuclear envelope assembled from multiple copies of approximately 30 different proteins called nucleoporins (Nups) that provide aqueous channels for nucleocytoplasmic transport during interphase. Although the structural aspects of NPCs have been characterized in detail, NPC formation and its regulation, especially during interphase, are poorly understood. In this study, using the temperature-sensitive RCC1 mutant tsBN2, a baby hamster kidney 21 cell line, we found that a lack of RCC1 activity inhibited NPC formation during interphase, suggesting that RanGTP is required for NPC formation during interphase in mammalian cells. Utilizing the reversible RCC1 activity in tsBN2 cells, we established a live-cell system that allows for the inhibition or initiation of NPC formation by changes in temperature. Our system enables the examination of NPC formation during interphase in living cells. As a lack of RCC1 decreased some Nups containing unstructured phenylalanine-glycine repeats in the NPC structure, we propose that RCC1 is also involved in maintaining NPC integrity during interphase in mammalian cells.