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BMC Dev Biol. 2008 Jan 28;8:10. doi: 10.1186/1471-213X-8-10.

Bunched, the Drosophila homolog of the mammalian tumor suppressor TSC-22, promotes cellular growth.

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1
Institute of Molecular Systems Biology, ETH Zürich, Wolfgang-Pauli-Str, 16, 8093 Zürich, Switzerland. gluderer@imsb.biol.ethz.ch

Abstract

BACKGROUND:

Transforming Growth Factor-beta1 stimulated clone-22 (TSC-22) is assumed to act as a negative growth regulator and tumor suppressor. TSC-22 belongs to a family of putative transcription factors encoded by four distinct loci in mammals. Possible redundancy among the members of the TSC-22/Dip/Bun protein family complicates a genetic analysis. In Drosophila, all proteins homologous to the TSC-22/Dip/Bun family members are derived from a single locus called bunched (bun).

RESULTS:

We have identified bun in an unbiased genetic screen for growth regulators in Drosophila. Rather unexpectedly, bun mutations result in a growth deficit. Under standard conditions, only the long protein isoform BunA - but not the short isoforms BunB and BunC - is essential and affects growth. Whereas reducing bunA function diminishes cell number and cell size, overexpression of the short isoforms BunB and BunC antagonizes bunA function.

CONCLUSION:

Our findings establish a growth-promoting function of Drosophila BunA. Since the published studies on mammalian systems have largely neglected the long TSC-22 protein version, we hypothesize that the long TSC-22 protein is a functional homolog of BunA in growth regulation, and that it is antagonized by the short TSC-22 protein.

PMID:
18226226
PMCID:
PMC2253523
DOI:
10.1186/1471-213X-8-10
[Indexed for MEDLINE]
Free PMC Article
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