Research / Clinical Summary

Michael Rosenfeld, MD Professor, Medicine Cancer Biology Program Contact by Email

The Rosenfeld lab is investigating integrative nuclear strategies responsible for orchestrating programs of genome-wide transcriptional responses to diverse signaling systems, including the new endocrine system, critical for physiological and behavioral processes in all vertebrates. His work continued to reveal unexpected gene-specific strategies that link regulated gene responses to other cellular response programs, including DNA damage/repair and development. Defining these strategies has suggested new approaches to diseases, including growth defects, diabetes, and several prevalent forms of cancer.

Recent studies have revealed that intrinsic enzymatic activities in a diverse network of coactivator and corepressor complexes, acting as “sensor” to permit integration of multiple signaling pathways modulate, reorganize and fine tune patterns of transcriptional response. Unexpected aspects of hormonal regulation of gene expression include a previously unrecognized occurrence of transient double-stranded DNA cleavage as a required component of regulated gene transcription and the identification of non-coding RNAs act as ligands regulating specific gene activation and repression programs.

Definition of a complex coregulatory network has permitted the recognition and definition of combinatorial codes for regulation of specific cohorts of gene targets. New genome-wide approaches have been developed that have uncovered a series of novel mechanisms, which permit the complex transcriptional response programs required for all metazoans, and elucidating these programs has provided insights into development and disease.

Recent projects include: An unexpected and general strategy has been uncovered, based on the requirement for specific cohorts of inhibitory histone methyltransferases (HMTs) to impose gene-specific “gatekeeper” functions that prevent unliganded nuclear receptors, and other classes of regulated transcription factors, from binding to their target gene promoters and causing constitutive gene activation in the absence of stimulating signals. This strategy, in part, is based on an HMT-dependent inhibitory histone code, as well as methylation of other regulatory targets, and imposes a requirement for specific histone demethylases, including LSD1, to permit ligand- and signal-dependent activation of regulated gene expression. These events link an inhibitory methylation activity including histone code, to a broadly-used strategy that circumvents pathological constitutive gene induction by physiologically-regulated transcription factors.

Opposing LSD1 Complexes in Gene Activation and Repression Programs in the Neuroendocrine System: Precise control of transcriptional programs underlying metazoan development is modulated by enzymatically active co-regulatory complexes, coupled with epigenetic strategies, how specific members of histone modification enzyme families such as histone methyltransferases and demethylases are utilized in vivo to orchestrate distinct developmental gene activation and repression programs remain unclear. A conditional gene deletion strategy was used to investigate functions of LSD1 in development of the anterior pituitary gland, as a well understood model of organogenesis, we found that LSD1, a component of the CoREST/CtBP corepressor complex, is required for late cell-lineage determination and differentiation during pituitary organogenesis. Intriguingly, LSD1-dependent gene repression programs can be extended late in development with the induced expression of a Krüpple-like repressor that acts as a molecular beacon for recruitment of the LSD1-containing CtBP/CoREST corepressor complex, causing repression of an additional cohort of genes, such as gene enhancer, that previously required LSD1 for activation. LSD1, thus regulates specific developmental programs in the window following initial organ commitment and prior to cell type differentiation based on a dynamic developmental regulation, with LSD1 serving initially as a key component of opposing coactivator and corepressor complexes that are recruited in a gene-specific fashion required for dictating specific programs of gene expression during mammalian organogenesis.

Signaling Pathways in Development: While the biological roles of canonical Wnt/b-catenin signaling in development and disease are well documented, understanding the molecular logic underlying the functionally-distinct nuclear transcriptional programs mediating the diverse functions of b-catenin remains a major challenge. Analysis of pituitary organogenesis has revealed an unexpected strategy for b-catenin-dependent regulation of cell lineage determination, based on interactions between a b-catenin and a specific homeodomain factor, Prop1, rather than Lef/Tcfs.

Sustained Notch activity has proven to be required for the temporal maintenance of specific cohorts of proliferating precursors in the developing pituitary gland, which underlies the ability to specify late-arising cell lineages. Conditional deletion of the major mediator of the Notch pathway, CSL/Rbp-J, leads to premature differentiation of progenitor cells and conversion of the late (Pit1) lineage into the early (corticotrope) lineage. Sustained Notch signaling in progenitor cells is required to prevent conversion of the late-arising cell lineages to early-born cell lineages, permitting specification of diverse cell types in mammalian organogenesis.

Macrophage: Cancer Cell Interactions: Androgens, acting via androgen receptors, are essential for growth of the normal prostate gland, and prostate cancer. While selective androgen receptor antagonists/ modulators (SARMs) are initially effective in treatment of prostate cancer, there is a rapid invariant resistance with progression from androgen-dependent to androgen-independent growth. Our studies have revealed that a subset of NF-kB-regulated genes, including a key metastasis suppressor gene, KAI1, can be derepressed in response to pro-inflammatory cytokines produced by activated macrophages. Based on these findings, we identified robust direct interactions between macrophages and prostate cell lines, with virtually 100% of samples in prostate cancer tissue arrays exhibiting specific macrophage: cancer cell interactions.

These interactions mediate a switch in function of SARMS from repression to activation in vivo. This is based on the selective presence of an evolutionarily-conserved receptor N terminal helical motif in sex steroid receptors, that modulates recruitment of a factor (TAB2), as a component of the N CoR corepressor complex. TAB2 serves as a molecular beacon for recruitment of a protein kinase, MEKK1, which mediates dismissal of the N CoR complex, causing derepression of androgen and estrogen receptor target genes. Peptides corresponding to the helical motif of AR or ERa receptors can block macrophage-dependent resistance, suggesting that nonpeptidergic orthologues might act to prevent inflammatory cytokine-dependent switch in SARM or SERM function and hence “block” resistance. Liganded SUMOylated nuclear receptors, including PPARy and LXR, are recruited to NCoR/SMRT corepressor complexes to transrepress gene programs activated by inflammatory cytokines, based on blocking recruitment of Ubc5 ubiquitylation machinery required for dismissal of the corepressor complex, providing potential new therapeutic approaches for treatment of prostate cancer.

Selected Publications:
Garcia-Bassets I, Y-S Kwon, F Telese, GG Prefontaine, K Hutt, CS Cheng, B-G Ju, KA Ohgi, J Wang, L Escoubet-Lozach, DW Rose, CK Glass, X-D Fu and MG Rosenfeld. Histone methylation-dependent mechanisms impose ligand dependency for gene ativaton by nuclear receptors. Cell 128(3):505-18 (2007).

Wang J, K Scully, X Zhu, L Cai, J Zhang, G Prefontaine, A Krones, KA Ohgi, P Zhu, I Garcia-Bassets, F Liu, H Taylor, J Lozach, FL Jayes, KS Korach, CK Glass, X-D, Fu and MG Rosenfeld. Opposing LSD1 complexes function in developmental gene activation and repression programs. Nature 446(7138):882-7 (2007).

Ju, B-G, VV Lunyak, V Perissi, I Garcia-Bassets, DW Rose, CK Glass and MG Rosenfeld. A Topoisomerase II-mediated dsDNA break required for regulated transcription. Science 312:1798-1802 (2006).

Olson LE, J Tollkuhn, C Scafoglio, A Krones, J Zhang, KA Ohgi, W Wu, MM Taketo, R Kemler, R Grosschedl, D Rose, X Li and MG Rosenfeld. Homeodomain-mediated beta-catenin-dependent switching events dictate cell-lineage determination. Cell 125:593-605 (2006).

Zhu P, SH Baek, EM Bourk, KA Ohgi, I Garcia-Bassets, H Sanjo, S Akira, PF Kotol, CK Glass, MG Rosenfeld and DW Rose. Macrophage/cancer cell interactions mediate hormone resistance by a nuclear receptor derepression pathway. Cell 124:615-29 (2006).

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