Subcellular localization of ankyrin repeats cofactor-1 regulates its corepressor activity

Identification and functional characterization of a bipartite nuclear localization signal in ANKRD11

ANKRD11 gene encodes for the large nuclear protein essential for multiple system development including the nervous system. However, the molecular basis for the proper nuclear localization of ANKRD11 has not yet been elucidated. In this study, we have identified a functional bipartite nuclear localization signal (bNLS) between residues 53 and 87 of ANKRD11. Using biochemical approaches, we discovered two major binding sites in this bipartite NLS for Importin α1. Through site-directed mutagenesis and functional analysis, we further found that this bipartite NLS is sufficient for nuclear import of overexpressing GFP in HeLa cells and necessary for nuclear localization of ANKRD11. Importantly, our study provides a possible pathogenic mechanism for certain clinical variants located within the bipartite nuclear localization signal of ANKRD11.

Histone deacetylase-3: Friend and foe of the brain

IMPACT STATEMENT

Brain development and degeneration are highly complex processes that are regulated by a large number of molecules and signaling pathways the identities of which are being unraveled. Accumulating evidence points to histone deacetylases and epigenetic mechanisms as being important regulators of these processes. In this review, we describe that histone deacetylase-3 (HDAC3) is a particularly crucial regulator of both neurodevelopment and neurodegeneration. In addition, HDAC3 regulates memory formation, synaptic plasticity, and the cognitive impairment associated with normal aging. Understanding how HDAC3 functions contributes to the normal development and functioning of the brain while also promoting neurodegeneration could lead to the development of therapeutic approaches for neurodevelopmental, neuropsychiatric, and neurodegenerative disorders.

Ankrd11 is a chromatin regulator involved in autism that is essential for neural development

Ankrd11 is a potential chromatin regulator implicated in neural development and autism spectrum disorder (ASD) with no known function in the brain. Here, we show that knockdown of Ankrd11 in developing murine or human cortical neural precursors caused decreased proliferation, reduced neurogenesis, and aberrant neuronal positioning. Similar cellular phenotypes and aberrant ASD-like behaviors were observed in Yoda mice carrying a point mutation in the Ankrd11 HDAC-binding domain. Consistent with a role for Ankrd11 in histone acetylation, Ankrd11 was associated with chromatin and colocalized with HDAC3, and expression and histone acetylation of Ankrd11 target genes were altered in Yoda neural precursors. Moreover, the Ankrd11 knockdown-mediated decrease in precursor proliferation was rescued by inhibiting histone acetyltransferase activity or expressing HDAC3. Thus, Ankrd11 is a crucial chromatin regulator that controls histone acetylation and gene expression during neural development, thereby providing a likely explanation for its association with cognitive dysfunction and ASD.

Clinical significance of Ankyrin repeat domain 12 expression in colorectal cancer

Background

Ankyrin repeat domain 12 (ANKRD12), is encoding a 224 kDa nuclear protein and most conserved at its N-terminal ankyrin repeats region and the C-terminal co-activator interacting domain. The aim of this study was to investigate the ANKRD12 mRNA expression in colorectal cancer (CRC) tumor tissues and the normal adjacent mucosa and its potential relevance to clinicopathological characteristics and prognosis.

Methods

Surgical specimens of tumor tissues (n = 68) and adjacent normal mucosa (n = 51) were obtained from CRC patients. The ANKRD12 mRNA expression was measured by quantitative real time reverse transcriptase polymerase chain reaction. The relationship between ANKRD12 mRNA expression and clinicopathological features was analyzed by appropriate statistics. Kaplan–Meier analysis and Cox proportional hazards regression models were used to investigate the correlation between ANKRD12 expression and prognosis of CRC patients.

Results

The relative mRNA expression of ANKRD12 were significantly lower in CRC tumor tissues than in the normal adjacent mucosa (P < 0.001), and the cases with low ANKRD12 expression showed a higher frequency of liver metastasis (P = 0.015). Kaplan–Meier analysis indicated that patients (CRC without liver metastasis) with low ANKRD12 expression had poor overall survival (P = 0.041). Multivariate analysis showed that low ANKRD12 expression was an independent predictor of overall survival.

Conclusion

This study revealed that ANKRD12 mRNA were down regulated in CRC tumor tissues and low ANKRD12 expression was correlated with liver metastasis and poor survival of CRC patients.

Regulation of ANKRD9 expression by lipid metabolic perturbations

Fatty acid oxidation (FAO) defects cause abnormal lipid accumulation in various tissues, which provides an opportunity to uncover novel genes that are involved in lipid metabolism. During a gene expression study in the riboflavin deficient induced FAO disorder in the chicken, we discovered the dramatic increase in mRNA levels of an uncharacterized gene, ANKRD9. No functions have been ascribed to ANKRD9 and its orthologs, although their sequences are well conserved among vertebrates. To provide insight into the function of ANKRD9, the expression of ANKRD9 mRNA in lipidperturbed paradigms was examined. The hepatic mRNA level of ANKRD9 was repressed by thyroid hormone (T(3)) and fasting, elevated by re-feeding upon fasting. However, ANKRD9 mRNA level is reduced in response to apoptosis. Transient transfection assay with green fluorescent protein tagged- ANKRD9 showed that this protein is localized within the cytoplasm. These findings point to the possibility that ANKRD9 is involved in intracellular lipid accumulation. [BMB reports 2009; 42(9): 568-573].

Identification of ANKRD11 as a p53 coactivator

The ability of p53 to act as a transcription factor is critical for its function as a tumor suppressor. Ankyrin repeat domain 11, ANKRD11 (also known as ANR11 or ANCO1), was found to be a novel p53-interacting protein that enhanced the transcriptional activity of p53. ANKRD11 expression was shown to be downregulated in breast cancer cell lines. Restoration of ANKRD11 expression in MCF-7 (wild-type p53) and MDA-MB-468 (p53(R273H) mutant) cells suppressed their proliferative and clonogenic properties through enhancement of CDKN1A (p21(waf1)/CIP1) expression. ShRNA-mediated silencing of ANKRD11 expression reduced the ability of p53 to activate CDKN1A expression. ANKRD11 was shown to associate with the p53 acetyltransferases and cofactors, P/CAF and hADA3. Exogenous ANKRD11 expression enhanced the levels of acetylated p53 in both MCF-7 and MDA-MB-468 cells. ANKRD11 enhanced the DNA-binding properties of mutant p53(R273H) to the CDKN1A promoter, suggesting that ANKRD11 can mediate the restoration of normal p53 function in some cancer-related p53 mutations. In addition, ANKRD11 itself was found to be a novel p53 target gene. These findings demonstrate a role for ANKRD11 as a p53 coactivator and suggest the involvement of ANKRD11 in a regulatory feedback loop with p53.

Ankyrin repeats-containing cofactors interact with ADA3 and modulate its co-activator function

ANCO (ankyrin repeats-containing cofactor)-1 and ANCO-2 are a family of unique transcriptional co-regulators with dual properties: they interact with both the co-activators and the co-repressors [Zhang, Yeung, Li, Tsai, Dinh, Wu, Li and Chen (2004) J. Biol. Chem. 279, 33799-33805]. Specifically, ANCO-1 is thought to recruit HDACs (histone deacetylases) to the p160 co-activator to repress transcriptional activation by nuclear receptors. In the present study, we provide new evidence to suggest further that ANCO-1 and ANCO-2 also interact with the co-activator ADA3 (alteration/deficiency in activation 3). The interaction occurs between the conserved C-terminal domain of ANCO-1 and the N-terminal transactivation domain of ADA3. Several subunits of the P/CAF {p300/CBP [CREB (cAMP-response-element-binding protein)-binding protein]-associated factor} complex, including ADA3, ADA2alpha/beta and P/CAF, showed co-localization with ANCO-1 nuclear dots, indicating an in vivo association of ANCO-1 with the P/CAF complex. Furthermore, a transient reporter assay revealed that both ANCO-1 and ANCO-2 repress ADA3-mediated transcriptional co-activation on nuclear receptors, whereas ANCO-1 stimulated p53-mediated transactivation. These data suggest that ADA3 is a newly identified target of the ANCO proteins, which may modulate co-activator function in a transcription-factor-specific manner.