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Molecular and Cellular Biology

Houston, Texas

Image 1: Ovulated mouse cumulus cell oocyte complex immunostained for matrix proteins hyaluronan and versican. By JoAnne Richards, Ph.D.; Image 2: By Yi LI, Ph.D.; Image 3: Mouse oocyte at meiosis I immunostained  for tubulin (red) phosphop38MAPK (green) and DNA (blue). By JoAnne Richards,  Ph.D.;  Image 4: Expanded cumulus cell ooctye ocmplex  immunostained for hyaluronan (red), TSG6 (green) and DAN (blue). By JoAnne  Richards, Ph.D.;  Image 5: Epithelial cells taken from a mouse  mammary gland were cultured in a dish and transduced with a retrovirus  expressing two genes. The green staining shows green fluorescent protein and the red  staining shows progesterone receptor expression. The nucleus of each cell is  stained blue. Photomicrograph taken at 200X magnification.  By Sandra L. Grimm,  Ph.D.; Image 6: Ovarian vasculature (red) is excluded from the granulosa cells (blue) within growing follicles (round structures); Image 7:  Ovulated mouse cumulus cell oocyte  complex immunostained for matrix proteins hyaluronan and versican. By JoAnne Richards, Ph.D.
Department of Molecular and Cellular Biology
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Xin-Hua Feng, Ph.D.

Xin-Hua Feng, Ph.D. photoProfessor
Departments of Molecular and Cellular Biology and Surgery


Ph.D.: University of Maryland, College Park
Postdoctoral training: University of California, San Francisco

Research Interest

Proteins Modifications and Signaling Networks in Cell Growth Control, Tumorigenesis and Development
My research is aimed at elucidating the underlying mechanisms and interplays among protein modifications, signaling pathways and gene transcription as well as understanding their roles in cell proliferation, tissue differentiation and pathogenesis of human diseases. Our current research projects include:

1. Phosphatome - genome-wide investigation of protein dephosphorylation: Signal transduction pathways are often regulated by dynamic interplay between protein kinases and phosphatases. Availability of all human protein serine/threonine phosphatases enables us to systematically investigating dephosphorylation of key proteins involved in cell signaling and cell functions. Genetic disruption of individual phosphatases is under way to elucidate the in vivo functions of phosphatases during development.

2. SUMO, ubiquitin and control of protein turnover/functions: We examine posttranslational modifications, particularly ubiquitination and SUMOylation of transcription factors in normal and cancer cells, and attempt to understand the molecular mechanisms for how the ubiquitination/proteasome and SUMOylation systems are regulated by environmental and developmental cues. Our study will provide insights into the relationship of protein deregulation with human cancers or abnormal development.

3. TGF-ß/BMP signal transduction: SMADs are evolutionarily conserved signal transducers and transcription factors controlling functions of TGF-ß/BMP. A large number of inactivating mutations on SMADs have been linked to human cancers and genetic diseases. We address these molecular interactions, requirement and functionality of SMADs in TGF-ß/BMP responses using cell biological, genomic and proteomic approaches. We investigate how SMADs mediate transcription and how their actions become terminated. We also study how SMADs as tumor suppressors interplay with oncogenic pathways, with particular interests in pancreatic, breast cancers, and lymphoma using in vitro and in vivo model systems.

4. Genetic screens, BMP/TGF-ß signaling, and ES cells: We are taking genome-wide approaches (e.g. genetic screens using lentiviral RNAi library) to identify novel TGF-ß signal modifiers or regulators involved in stem cell differentiation. Novel molecules that control TGF-ß/BMP signaling or participate in human ES cell self-renewal and differentiation will be further studied in vitro and in model organisms to define their physiological roles in tissue differentiation and organ development.

5. Immune suppression by TGF-ß: TGF-ß is a major inflammatory and immune-regulatory cytokine, but the mechanism how TGF-ß exerts its actions is unclear. We are interested in investigating the signaling interactions between TGF-ß pathway and other cytokine pathways (such as TNF-alpha, IL-1, IL-6 pathways) in immune responses. This area of research may lead to drug discovery for cancer and inflammatory diseases.

Contact Information

Baylor College of Medicine
One Baylor Plaza, Room R712
Houston, TX 77030

Phone: 713-798-4756

Selected Publications

  1. Dai F, Lin X, Chang C, and Feng X-H (2009). Nuclear export of Smad2 and Smad3 by RanBP3 facilitates termination of TGF-ß signaling. Dev. Cell, 16:345-357.
  2. Wrighton K, Lin X, Feng X-H. (2008). Critical role of chaperone HSP90 in TGF-ß signaling. Proc. Natl. Acad. Sci. USA, 105: 9244-9249.
  3. Wang D*, Long J*, Dai F, Liang M, Feng X-H, and Lin X. (2007). Bcl6 represses Smad signaling in TGF-ß resistance. Cancer Res., 68: 783-789.
  4. Dai F, Chang C, Lin X, Dai G, Mei L, and Feng X-H. (2007). Erbin inhibits TGF-ß signaling through a novel Smad-interacting domain. Mol. Cell. Biol., 27: 6183-6194.
  5. Wrighton K, Willis D, Long J, Liu F, Lin X, and Feng X-H. (2006). Small carboxy-terminal domain phosphatases dephosphorylate the regulatory linker regions of Smad2 and Smad3 to enhance TGF-ß signaling. J. Biol. Chem., 281: 38365–38375.
  6. Lin X*, Duan X*, Liang Y-Y*, Su Y*, Wrighton K, Hu M, Long J, Davis C, Wang J, Brunicardi FC, Shi Y, Chen YG, Meng A, and Feng X-H. (2006). PPM1A functions a Smad phosphatase to terminate TGF-ß signaling. Cell, 125: 915-928.
  7. Feng X-H and Derynck R. (2005). Specificity and versatility of TGF-ß signaling through Smads. Annu. Rev. Cell Dev. Biol., 12: 659-693.
  8. Liang M, Y-Y. Liang, Wrighton K, Ungermannova D, Wang X, Brunicardi FC, X. Liu, Feng X-H and Lin X. (2004). Ubiquitination and proteolysis of cancer-derived Smad4 mutants by SCFSkp2. Mol. Cell. Biol., 24: 7524-7537.
  9. Lin X, Sun B, Liang M, Liang Y-Y, Gast A, Hildebrand J, Brunicardi FC, Melchior F and Feng X-H. (2003) Opposed regulation of CtBP corepressor function by SUMOylation and PDZ binding. Mol. Cell, 11:1389-1396.
  10. Feng X-H, Liang Y-Y, Liang M, Zhai W and Lin X. (2002) Direct interaction of c-Myc with Smad2 and Smad3 to inhibit TGF-ß-mediated induction of the CDK inhibitor p15. Mol. Cell, 9:133-143.

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