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Scaling the Drosophila Wing: TOR-Dependent Target Gene Access by the Hippo Pathway Transducer Yorkie.

Parker J, Struhl G - PLoS Biol. (2015)

Bottom Line: Here, we show that the TOR pathway regulates Yki by a separate and novel mechanism in the Drosophila wing.Instead of controlling Yki nuclear access, TOR signaling governs Yki action after it reaches the nucleus by allowing it to gain access to its target genes.When TOR activity is inhibited, Yki accumulates in the nucleus but is sequestered from its normal growth-promoting target genes--a phenomenon we term "nuclear seclusion." Hence, we posit that in addition to its well-known role in stimulating cellular metabolism in response to nutrients, TOR also promotes wing growth by liberating Yki from nuclear seclusion, a parallel pathway that we propose contributes to the scaling of wing size with nutrient availability.

View Article: PubMed Central - PubMed

Affiliation: Department of Genetics and Development, Columbia University, New York, New York, United States of America; Division of Biology, Imperial College London, London, United Kingdom.

ABSTRACT
Organ growth is controlled by patterning signals that operate locally (e.g., Wingless/Ints [Wnts], Bone Morphogenetic Proteins [BMPs], and Hedgehogs [Hhs]) and scaled by nutrient-dependent signals that act systemically (e.g., Insulin-like peptides [ILPs] transduced by the Target of Rapamycin [TOR] pathway). How cells integrate these distinct inputs to generate organs of the appropriate size and shape is largely unknown. The transcriptional coactivator Yorkie (Yki, a YES-Associated Protein, or YAP) acts downstream of patterning morphogens and other tissue-intrinsic signals to promote organ growth. Yki activity is regulated primarily by the Warts/Hippo (Wts/Hpo) tumour suppressor pathway, which impedes nuclear access of Yki by a cytoplasmic tethering mechanism. Here, we show that the TOR pathway regulates Yki by a separate and novel mechanism in the Drosophila wing. Instead of controlling Yki nuclear access, TOR signaling governs Yki action after it reaches the nucleus by allowing it to gain access to its target genes. When TOR activity is inhibited, Yki accumulates in the nucleus but is sequestered from its normal growth-promoting target genes--a phenomenon we term "nuclear seclusion." Hence, we posit that in addition to its well-known role in stimulating cellular metabolism in response to nutrients, TOR also promotes wing growth by liberating Yki from nuclear seclusion, a parallel pathway that we propose contributes to the scaling of wing size with nutrient availability.

No MeSH data available.


Related in: MedlinePlus

TOR inhibition reduces Yki target gene expression.Wing discs expressing GFP-NLS (green) under dpp.Gal4 control with (B, D, F, H), or without (A, C, E, G), coexpressing the TOR inhibitors TorTED, TSC1 and TSC2, as in Fig 3. TOR inhibition reduces the Yki targets DIAP1 protein (B), diap12B2C-lacZ (D) fj-lacZ (F) and ex-lacZ (H; kept for 8 hr at 29°C before dissection, to increase the level of TOR inhibition), all labelled in red (nuclei counterstained with Hoechst, blue).
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pbio.1002274.g004: TOR inhibition reduces Yki target gene expression.Wing discs expressing GFP-NLS (green) under dpp.Gal4 control with (B, D, F, H), or without (A, C, E, G), coexpressing the TOR inhibitors TorTED, TSC1 and TSC2, as in Fig 3. TOR inhibition reduces the Yki targets DIAP1 protein (B), diap12B2C-lacZ (D) fj-lacZ (F) and ex-lacZ (H; kept for 8 hr at 29°C before dissection, to increase the level of TOR inhibition), all labelled in red (nuclei counterstained with Hoechst, blue).

Mentions: Typically, nuclear Yki up-regulates growth-promoting target genes, one of the best characterized of these being diap1, the gene encoding the Drosophila Inhibitor of Apoptosis protein [18,19]. However, the dramatic increase in nuclear Yki accumulation caused by TOR inhibition (Fig 3C and 3D) is associated with a strong reduction in DIAP protein levels (Fig 4A and 4B), consistent with reduced diap1 gene transcription. Diap1 transcription is normally driven by a Yki-Sd complex that binds ~4 kb downstream of the transcription start site of the predominant diap1-RA transcript [19]. A minimal reporter construct, 2B2C-lacZ, containing ~300 bp of this enhancer region, is up-regulated by Yki overactivation [19]. Conversely, RNAi knockdown of Yki results in reduced 2B2C-lacZ expression (S4A and S4A’ Fig). Like Yki RNAi knockdown, TOR inhibition caused a marked decrease in 2B2C-lacZ expression (Fig 4C and 4D), indicating a failure of the Yki/Sd-dependent 2B2C enhancer to maintain normal target gene expression.


Scaling the Drosophila Wing: TOR-Dependent Target Gene Access by the Hippo Pathway Transducer Yorkie.

Parker J, Struhl G - PLoS Biol. (2015)

TOR inhibition reduces Yki target gene expression.Wing discs expressing GFP-NLS (green) under dpp.Gal4 control with (B, D, F, H), or without (A, C, E, G), coexpressing the TOR inhibitors TorTED, TSC1 and TSC2, as in Fig 3. TOR inhibition reduces the Yki targets DIAP1 protein (B), diap12B2C-lacZ (D) fj-lacZ (F) and ex-lacZ (H; kept for 8 hr at 29°C before dissection, to increase the level of TOR inhibition), all labelled in red (nuclei counterstained with Hoechst, blue).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4608745&req=5

pbio.1002274.g004: TOR inhibition reduces Yki target gene expression.Wing discs expressing GFP-NLS (green) under dpp.Gal4 control with (B, D, F, H), or without (A, C, E, G), coexpressing the TOR inhibitors TorTED, TSC1 and TSC2, as in Fig 3. TOR inhibition reduces the Yki targets DIAP1 protein (B), diap12B2C-lacZ (D) fj-lacZ (F) and ex-lacZ (H; kept for 8 hr at 29°C before dissection, to increase the level of TOR inhibition), all labelled in red (nuclei counterstained with Hoechst, blue).
Mentions: Typically, nuclear Yki up-regulates growth-promoting target genes, one of the best characterized of these being diap1, the gene encoding the Drosophila Inhibitor of Apoptosis protein [18,19]. However, the dramatic increase in nuclear Yki accumulation caused by TOR inhibition (Fig 3C and 3D) is associated with a strong reduction in DIAP protein levels (Fig 4A and 4B), consistent with reduced diap1 gene transcription. Diap1 transcription is normally driven by a Yki-Sd complex that binds ~4 kb downstream of the transcription start site of the predominant diap1-RA transcript [19]. A minimal reporter construct, 2B2C-lacZ, containing ~300 bp of this enhancer region, is up-regulated by Yki overactivation [19]. Conversely, RNAi knockdown of Yki results in reduced 2B2C-lacZ expression (S4A and S4A’ Fig). Like Yki RNAi knockdown, TOR inhibition caused a marked decrease in 2B2C-lacZ expression (Fig 4C and 4D), indicating a failure of the Yki/Sd-dependent 2B2C enhancer to maintain normal target gene expression.

Bottom Line: Here, we show that the TOR pathway regulates Yki by a separate and novel mechanism in the Drosophila wing.Instead of controlling Yki nuclear access, TOR signaling governs Yki action after it reaches the nucleus by allowing it to gain access to its target genes.When TOR activity is inhibited, Yki accumulates in the nucleus but is sequestered from its normal growth-promoting target genes--a phenomenon we term "nuclear seclusion." Hence, we posit that in addition to its well-known role in stimulating cellular metabolism in response to nutrients, TOR also promotes wing growth by liberating Yki from nuclear seclusion, a parallel pathway that we propose contributes to the scaling of wing size with nutrient availability.

View Article: PubMed Central - PubMed

Affiliation: Department of Genetics and Development, Columbia University, New York, New York, United States of America; Division of Biology, Imperial College London, London, United Kingdom.

ABSTRACT
Organ growth is controlled by patterning signals that operate locally (e.g., Wingless/Ints [Wnts], Bone Morphogenetic Proteins [BMPs], and Hedgehogs [Hhs]) and scaled by nutrient-dependent signals that act systemically (e.g., Insulin-like peptides [ILPs] transduced by the Target of Rapamycin [TOR] pathway). How cells integrate these distinct inputs to generate organs of the appropriate size and shape is largely unknown. The transcriptional coactivator Yorkie (Yki, a YES-Associated Protein, or YAP) acts downstream of patterning morphogens and other tissue-intrinsic signals to promote organ growth. Yki activity is regulated primarily by the Warts/Hippo (Wts/Hpo) tumour suppressor pathway, which impedes nuclear access of Yki by a cytoplasmic tethering mechanism. Here, we show that the TOR pathway regulates Yki by a separate and novel mechanism in the Drosophila wing. Instead of controlling Yki nuclear access, TOR signaling governs Yki action after it reaches the nucleus by allowing it to gain access to its target genes. When TOR activity is inhibited, Yki accumulates in the nucleus but is sequestered from its normal growth-promoting target genes--a phenomenon we term "nuclear seclusion." Hence, we posit that in addition to its well-known role in stimulating cellular metabolism in response to nutrients, TOR also promotes wing growth by liberating Yki from nuclear seclusion, a parallel pathway that we propose contributes to the scaling of wing size with nutrient availability.

No MeSH data available.


Related in: MedlinePlus