title: E3 ubiquitin ligase RFWD2 controls lung branching through protein-level regulation of ETV transcription factors.
abstract: The mammalian lung is an elaborate branching organ, and it forms following a highly stereotypical morphogenesis program. It is well established that precise control at the transcript level is a key genetic underpinning of lung branching. In comparison, little is known about how regulation at the protein level may play a role. Ring finger and WD domain 2 (RFWD2, also termed COP1) is an E3 ubiquitin ligase that modifies specific target proteins, priming their degradation via the ubiquitin proteasome system. RFWD2 is known to function in the adult in pathogenic processes such as tumorigenesis. Here, we show that prenatal inactivation of Rfwd2 gene in the lung epithelium led to a striking halt in branching morphogenesis shortly after secondary branch formation. This defect is accompanied by distalization of the lung epithelium while growth and cellular differentiation still occurred. In the mutant lung, two E26 transformation-specific (ETS) transcription factors essential for normal lung branching, ETS translocation variant 4 (ETV4) and ETV5, were up-regulated at the protein level, but not at the transcript level. Introduction of Etv loss-of-function alleles into the Rfwd2 mutant background attenuated the branching phenotype, suggesting that RFWD2 functions, at least in part, through degrading ETV proteins. Because a number of E3 ligases are known to target factors important for lung development, our findings provide a preview of protein-level regulatory network essential for lung branching morphogenesis.
authors.affiliation: Laboratory of Genetics, Department of Medical Genetics, University of Wisconsin-Madison, Madison, WI 53706.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Laboratory of Genetics, Department of Medical Genetics, University of Wisconsin-Madison, Madison, WI 53706.
authors.forename: Shigetoshi
authors.initials: S
authors.lastname: Yokoyama
authors.affiliation: Laboratory of Genetics, Department of Medical Genetics, University of Wisconsin-Madison, Madison, WI 53706.
authors.forename: John C
authors.initials: JC
authors.lastname: Herriges
authors.affiliation: Laboratory of Genetics, Department of Medical Genetics, University of Wisconsin-Madison, Madison, WI 53706.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Laboratory of Genetics, Department of Medical Genetics, University of Wisconsin-Madison, Madison, WI 53706.
authors.forename: Randee E
authors.initials: RE
authors.lastname: Young
authors.affiliation: Laboratory of Genetics, Department of Medical Genetics, University of Wisconsin-Madison, Madison, WI 53706.
authors.forename: Jamie M
authors.initials: JM
authors.lastname: Verheyden
authors.affiliation: Laboratory of Genetics, Department of Medical Genetics, University of Wisconsin-Madison, Madison, WI 53706 xsun@wisc.edu.
authors.forename: Xin
authors.initials: X
authors.lastname: Sun
mesh_terms: D000818:Animals; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005260:Female; D053823:Hedgehog Proteins / Q000378:metabolism; D008168:Lung / Q000196:embryology* / Q000201:enzymology; D051379:Mice; D009024:Morphogenesis; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011247:Pregnancy; D050783:Proto-Oncogene Proteins c-ets / Q000378:metabolism; D020545:Respiratory Mucosa / Q000201:enzymology; D014157:Transcription Factors / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; C513242:Etv5 protein, mouse; D053823:Hedgehog Proteins; D009687:Nuclear Proteins; D050783:Proto-Oncogene Proteins c-ets; C465570:Shh protein, mouse; D014157:Transcription Factors; C471982:COP1 protein, mouse; D044767:Ubiquitin-Protein Ligases
keywords: COP1; E3 ubiquitin ligases; ETV transcription factors; RFWD2; lung branching