The transforming growth factor-β (TGF-β) family plays major pleiotropic roles by regulating many physiological processes in development and tissue homeostasis. The TGF-β signaling pathway outcome relies on the control of the spatial and temporal expression of >500 genes, which depend on the functions of the Smad protein along with those of diverse modulators of this signaling pathway, such as transcriptional factors and cofactors. Ski (Sloan-Kettering Institute) and SnoN (Ski novel) are Smad-interacting proteins that negatively regulate the TGF-β signaling pathway by disrupting the formation of R-Smad/Smad4 complexes, as well as by inhibiting Smad association with the p300/CBP coactivators. The Ski and SnoN transcriptional cofactors recruit diverse corepressors and histone deacetylases to repress gene transcription. The TGF-β/Smad pathway and coregulators Ski and SnoN clearly regulate each other through several positive and negative feedback mechanisms. Thus, these cross-regulatory processes finely modify the TGF-β signaling outcome as they control the magnitude and duration of the TGF-β signals. As a result, any alteration in these regulatory mechanisms may lead to disease development. Therefore, the design of targeted therapies to exert tight control of the levels of negative modulators of the TGF-β pathway, such as Ski and SnoN, is critical to restore cell homeostasis under the specific pathological conditions in which these cofactors are deregulated, such as fibrosis and cancer.

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Background: Human SKIL gene encodes for SNON, a negative regulator of the TGF-␤/SMAD pathway. Results: We provide a molecular mechanism of transcriptional regulation of SKIL gene expression by TGF-␤/SMADs. Conclusion: Transcriptional cofactor complex SNON-SMAD4 negatively controls the expression of SKIL gene. Significance: The formation and function of complex SNON-SMAD4 are impaired in cancer cells lacking SMAD4, which affects TGF ␤-target gene regulation.

Background: Estrogen receptor ␣ (ER␣) mediates the effects of 17␤-estradiol in mammary gland, and it is associated with the development of breast cancer tumors. Results: Tristetraprolin (TTP) represses ER␣ transactivation through its interaction with histone deacetylases. Conclusion:TTP acts as a novel ER␣ corepressor. Significance: TTP reduces estradiol-induced cell proliferation and tumor growth, suggesting it may be important in breast cancer development.

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More than 70% of all breast cancer cases are estrogen receptor alpha-positive (ERα). ERα is a member of the nuclear receptor family, and its activity is implicated in the gene transcription linked to the proliferation of breast cancer cells, as well as in extranuclear signaling pathways related to the development of resistance to endocrine therapy. Protein-protein interactions and posttranslational modifications of ERα underlie critical mechanisms that modulate its activity. In this review, the relationship between ERα and ubiquitin protein (Ub), was investigated in the context of breast cancer cells. Interestingly, Ub can bind covalently or non-covalently to ERα resulting in either a proteolytic or non-proteolytic fate for this receptor. Thereby, Ub-dependent molecular pathways that modulate ERα signaling may play a central role in breast cancer progression, and consequently, present critical targets for treatment of this disease.

Alzheimer disease (AD) is the primary form of dementia that occurs spontaneously in older adults. Interestingly, the epigenetic profile of the cells forming the central nervous system changes during aging and may contribute to the progression of some neurodegenerative diseases such as AD. In this review, we present general insights into relevant epigenetic mechanisms and their relationship with aging and AD. The data suggest that some epigenetic changes during aging could be utilized as biomarkers and target molecules for the prevention and control of AD.