The functional interactome landscape of the human histone deacetylase family

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Dynamic Regulation of Class IIa Histone Deacetylases by Phosphorylation

Histone deacetylases (HDACs) are critical regulators of host and viral transcription. HDACs carry out their transcriptional repressive activities through substrate deacetylation and participation in numerous multi-protein complexes. Within the HDAC family, class IIa enzymes (HDAC4/5/ 7/9) shuttle between the nucleus and cytoplasm in response to signal-dependent phosphorylations. Within the nucleus, class IIa HDACs interact with transcription factors, co-repressor complexes, and HDAC3 to repress transcription. However, the regulatory roles of numerous additional HDAC phosphorylations remain unexplored, and the functional roles of HDACs outside of the nucleus, during cell cycle progression, and during viral infection remain less poorly understood. In order to address these remaining questions regarding the function and regulation of class IIa HDACs, this study integrates mass spectrometry-based proteomics, phosphomutant analyses, in vitro enzymatic assays, microscopy, and cell cycle and viral infection studies. We present the first comprehensive protein interactome for HDACs 1-11 in T cells and highlight shared and unique roles for individual HDAC classes. We present a method for assessing protein interaction stabilities using stable isotope labeling in conjunction with a probabilistic scoring method for determination of interaction specificity using class IIa HDACs as a test case. We further focused our investigation of class IIa HDACs on HDAC5 and identified 14 novel phosphorylations on HDAC5. Generation of serine-to-alanine phosphomutant cell lines for individual sites revealed that phosphorylation of Ser279 within the NLS is important for HDAC5 nuclear localization. We further demonstrate that Ser278 is phosphorylated during mitosis by the kinase Aurora B. Aurora B-mediated phosphorylation of HDAC5 is conserved in HDAC4 and HDAC9, and targets class IIa HDACs to the midzone. During mitosis, HDAC5 exhibits diminished association with co-repressor components and limited in vitro deacetylation activity. Additional analysis of phosphorylations within functional domains of HDAC5 demonstrated that phosphorylation abundances range from ~3-75%, suggesting both dynamic and consitutive modification of individual sites. Together, these results demonstrate that HDAC5 functions are carefully coordinated by post-translational modifications and protein interactions. Finally, we profile the dynamic localization of HDAC5 during HIV-1 infection and accompanying changes in HDAC5 and HDAC3 interactions to gain preliminary insight into class IIa HDAC during viral infection

Exploring the Significance of Social Class Identity Performance in the English Classroom: A Case Study Analysis of a Literature Circle Discussion

English educators at all levels have endeavored to understand difference in their classrooms both in terms of the content that they teach and in terms of the social and cultural identities of students in their classrooms. However, although educators have come a long way in understanding identity as it is constituted by race and gender, much work is needed for social class identity to be understood with nuance and complexity. This article explores the salience of class identity as it affects one aspect of learning in the English classroom--literary interpretation. Specifically, this article draws on data from a six-week literature circle unit in which four white, socioeconomically diverse students discussed Dorothy Allison\u27s Bastard Out of Carolina . By examining and uncovering the students\u27 social class identity performances as they influenced both their participation and interpretations in the literature circle, this article sheds light on the significance of social class identity in the English classroom and makes a case for the importance of a more thorough consideration of social class in teaching and research in English education

Problematizing Literature Circles as Forums for Discussion of Multicultural and Political Texts

In a six-week literature circle unit in a tenth-grade classroom, one group of students discussed Dorothy Allison\u27s novel Bastard out of Carolina. By criteria frequently used to judge the quality of discussion, this literature circle was successful. However, several key moments are highlighted that point to the limits of literature circles as they are typically implemented for engaging students in the full critical depth of multicultural and political texts. Finally, suggestions are offered for rethinking literature circle pedagogy with the goal of offering students a more nuanced and robust experience with such texts

Post-translational Modifications Regulate Class IIa Histone Deacetylase (HDAC) Function in Health and Disease

Class IIa histone deacetylases (HDACs4, -5, -7, and -9) modulate the physiology of the human cardiovascular, musculoskeletal, nervous, and immune systems. The regulatory capacity of this family of enzymes stems from their ability to shuttle between nuclear and cytoplasmic compartments in response to signal-driven post-translational modification. Here, we review the current knowledge of modifications that control spatial and temporal histone deacetylase functions by regulating subcellular localization, transcriptional functions, and cell cycle-dependent activity, ultimately impacting on human disease. We discuss the contribution of these modifications to cardiac and vascular hypertrophy, myoblast differentiation, neuronal cell survival, and neurodegenerative disorders