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ING proteins interact with core histones through their plant homeodomains (PHDs) and with histone acetyltransferase (HAT) and histone deacetylase (HDAC) complexes to alter chromatin structure. Here we identify a lamin interaction domain (LID) found only in ING proteins, through which they bind to and colocalize with lamin A. Lamin knockout (LMNA(-/-)) cells show reduced levels of ING1 that mislocalize. Ectopic lamin A expression increases ING1 levels and re-targets it to the nucleus to act as an epigenetic regulator. ING1 lacking the LID does not interact with lamin A or affect apoptosis. In LMNA(-/-) cells, apoptosis is not affected by ING1. Mutation of lamin A results in several laminopathies, including Hutchinson-Gilford progeria syndrome (HGPS), a severe premature ageing disorder. HGPS cells have reduced ING1 levels that mislocalize. Expression of LID peptides to block lamin A-ING1 interaction induces phenotypes reminiscent of laminopathies including HGPS. These data show that targeting of ING1 to the nucleus by lamin A maintains ING1 levels and biological function. Known roles for ING proteins in regulating apoptosis and chromatin structure indicate that loss of lamin A-ING interaction may be an effector of lamin A loss, contributing to the HGPS phenotype.

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Members of the ING (inhibitor of growth) family of chromatin modifying proteins (ING1-ING5

Reolysin® is well tolerated given intralesionaly, with DLT/MTD not reached at a dose of 10(10) PFU. The favorable toxicity profile, lack of viral shedding and possible therapeutic activity has made this unattenuated oncolytic reovirus an attractive cancer therapeutic agent for ongoing clinical studies, including in the setting of locally advanced accessible disease for palliation of symptoms.

ING1b is well conserved and the major isoform expressed in human cells (14). Of the other INGs, p32ING2 shares the most sequence homology (23) and functional similarities with p33ING1b (12). Functional links have been found between the ING family of proteins and cellular processes important in tumorigenesis, including apoptosis, cell cycle regulation, senescence, and the DNA damage response. One major pathway through which the ING proteins exert these effects is through physically and functionally interacting with integral components of histone acetyltransferase-and histone deacetylase chromatin-modifying complexes (8,26,31,33,43,51,56) as well as binding preferentially to methylated histones through their plant homeodomains (PHD) (37,44,50). This has the effect of targeting these complexes to regulate local acetylation and deacetylation levels, which alters gene expression (15). The PHD (21) and/or a polybasic region downstream of the PHD (28) has also been shown to bind rare stress-induced phospholipids and to induce ING proteins to activate p53. It is interesting to note that the BRCA1 protein also impinges upon chromatin remodeling through interactions with BARD1 (3, 27, 39, 61), so both the ING1 and BRCA1 tumor suppressors may contribute to the emergence of cancers through similar mechanisms. Consistent with ING proteins altering chromatin structure, the expression of p21 and Bax is upregulated by p33ING1b , p32 ING2 , and p47 ING3 proteins in a number of cancer cell lines (29,40,41). Although a recent cDNA microarray analysis using the transformed mouse mammary epithelial cell line NMuMG did not register p21 or Bax as a target of ING1, it did identify more than a dozen other genes whose expression was altered in response to p33ING1b , including cyclin B1 and the DEK proto-oncogene (54).Heat shock proteins (HSPs) are a large family of evolutionarily conserved proteins which function as molecular chaperones (5). These specialized proteins play important roles in cellular defense mechanisms against protein aggregation and misfolding by binding nonnative states of other proteins and assisting them in reaching a correctly folded and functional conformation. They are also involved in protein translocation across membranes to different organelles for final packaging, degradation, or repair through their unfoldase activities (20,22). More than a dozen HSPs, such as HSP27, -40, -60, -70, -90, and -110, etc., have been identified so far, and they are named according to their molecular mass (5, 63). Among them, HSP70 is one of the most conserved, and it is also the best characterized. In most mammalian cells there are two prominent isoforms of HSP70, an abundant constitutive member called HSP73 and the highly stress-inducible HSP72. HSP70 isoform expression is enhanced by a number of different stress factors, including heat, cold, glucose, alcohol, heavy metals, and ischemia (38). Expression of HSP70 protects cells from stress (46) and is generally thought to play cytoprotective roles through antagonizing components ...

The INhibitor of Growth tumor suppressors (ING1-ING5) affect aging, apoptosis, DNA repair and tumorigenesis. Plant homeodomains (PHD) of ING proteins bind histones in a methylation-sensitive manner to regulate chromatin structure. ING1 and ING2 contain a polybasic region (PBR) adjacent to their PHDs that binds stress-inducible phosphatidylinositol monophosphate (PtIn-MP) signaling lipids to activate these INGs. ING1 induces apoptosis independently of p53 but other studies suggest proapoptotic interdependence of ING1 and p53 leaving their functional relationship unclear. Here we identify a novel ubiquitin-binding domain (UBD) that overlaps with the PBR of ING1 and shows similarity to previously described UBDs involved in DNA damage responses. The ING1 UBD binds ubiquitin with high affinity (Kd∼100 nM) and ubiquitin competes with PtIn-MPs for ING1 binding. ING1 expression stabilized wild-type, but not mutant p53 in an MDM2-independent manner and knockdown of endogenous ING1 depressed p53 levels in a transcription-independent manner. ING1 stabilized unmodified and six multimonoubiquitinated forms of wild-type p53 that were also seen upon DNA damage, but not p53 mutants lacking the six known sites of ubiquitination. We also find that ING1 physically interacts with herpesvirus-associated ubiquitin-specific protease (HAUSP), a p53 and MDM2 deubiquitinase (DUB), and knockdown of HAUSP blocks the ability of ING1 to stabilize p53. These data link lipid stress signaling to ubiquitin-mediated proteasomal degradation through the PBR/UBD of ING1 and further indicate that ING1 stabilizes p53 by inhibiting polyubiquitination of multimonoubiquitinated forms via interaction with and colocalization of the HAUSP-deubiquitinase with p53.

IntroductionThe serine/threonine protein kinase ataxia telangiectasia mutated (ATM) is critical in maintaining genomic integrity. Upon DNA double-strand breaks, ATM phosphorylates key downstream proteins including p53 and BRCA1/2, thereby orchestrating complex signaling pathways involved in cell cycle arrest, DNA repair, senescence and apoptosis. Although sporadic mutation of ATM occurs rarely in breast cancer, the status of its protein expression and its clinical significance in breast cancer remain not well established. Our study was designed to investigate the influence of ATM protein in both tumor and cancer-associated stroma on clinical outcome in hormone-positive (HPBC) and hormone-negative (HNBC) early-stage breast cancer (EBC).MethodsTissue microarrays (TMAs), containing formalin-fixed, paraffin-embedded resected tumors from two cohorts of patients (HPBC cohort: n = 130; HNBC cohort: n = 168) diagnosed at the Tom Baker Cancer Centre, Calgary, Canada, were analyzed for ATM protein expression using fluorescence immunohistochemistry (IHC) and automated quantitative analysis (AQUA). ATM expression levels were measured within the tumor as a whole (tATM) as indicated by pan-cytokeratin expression, tumor nuclear compartment (nATM) as indicated by both DAPI and pan-cytokeratin-positive results, and cancer-associated stroma (csATM) as indicated by vimentin-positive and pan-cytokeratin-negative results. ATM expression levels within these compartments were correlated with clinical outcome.ResultsWhile tATM and nATM were significantly lower in tumors compared to normal breast epithelial tissues, csATM was significantly higher than the corresponding normal tissue compartment. In addition, the median expression level of both tATM and nATM were two- to threefold lower (P <0.001) in HNBC than in HPBC. In both HNBC and HPBC cohorts, patients with low tATM, nATM and csATM tumors had significantly poorer survival outcomes than those with a high tATM, nATM and csATM, but this effect was more pronounced in HNBC. A multivariate analysis demonstrates that these biomarkers predict survival independent of tumor size and lymph node status, but only in the HNBC cohort (P <0.001).ConclusionsLow ATM protein expression in both malignant tumor and stromal compartments likely contributes to the aggressive nature of breast cancer and is an independent prognostic factor associated with worse survival in HNBC patients.Electronic supplementary materialThe online version of this article (doi:10.1186/s13058-015-0575-2) contains supplementary material, which is available to authorized users.