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Ectopic expression of Zmiz1 induces cutaneous squamous cell malignancies in a mouse model of cancer.

Rogers LM, Riordan JD, Swick BL, Meyerholz DK, Dupuy AJ - J. Invest. Dermatol. (2013)

Bottom Line: Here we show that transposon-induced mutations in Zmiz1 drive expression of a truncated transcript that is similar to an alternative endogenous ZMIZ1 transcript found to be overexpressed in human SCCs relative to normal skin.In addition, we found that the alternative Zmiz1 isoform has greater protein stability than its full-length counterpart.Finally, we provide evidence that ZMIZ1 is overexpressed in a significant percentage of human breast, ovarian, and colon cancers in addition to human SCCs, suggesting that ZMIZ1 may play a broader role in epithelial cancers.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy and Cell Biology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA.

ABSTRACT
Cutaneous squamous cell carcinoma (SCC) is the second most common form of cancer in the human population, yet the underlying genetic mechanisms contributing to the disease are not well understood. We recently identified Zmiz1 as a candidate oncogene in nonmelanoma skin cancer through a transposon mutagenesis screen. Here we show that transposon-induced mutations in Zmiz1 drive expression of a truncated transcript that is similar to an alternative endogenous ZMIZ1 transcript found to be overexpressed in human SCCs relative to normal skin. We also describe an original mouse model of invasive keratoacanthoma driven by skin-specific expression of the truncated Zmiz1 transcript. Unlike most mouse models, Zmiz1-induced skin tumors develop rapidly and in the absence of promoting agents such as phorbol esters. In addition, we found that the alternative Zmiz1 isoform has greater protein stability than its full-length counterpart. Finally, we provide evidence that ZMIZ1 is overexpressed in a significant percentage of human breast, ovarian, and colon cancers in addition to human SCCs, suggesting that ZMIZ1 may play a broader role in epithelial cancers.

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Zmiz1Δ1-185 displays increased protein stabilityWestern blots show higher steady-state protein expression in Zmiz1Δ1-185-HA-expressing HeLa, MCF7, and N-HSK-1 cells than those stably expressing full-length Zmiz1-HA, despite lacking significant differential transcript expression as analyzed by qRT-PCR (data not shown). Where indicated, MG132 (20μm) treatment increased protein stability, suggesting Zmiz1 and Zmiz1Δ1-185 are degraded by the proteasome and that stability is regulated at the protein level.
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Figure 4: Zmiz1Δ1-185 displays increased protein stabilityWestern blots show higher steady-state protein expression in Zmiz1Δ1-185-HA-expressing HeLa, MCF7, and N-HSK-1 cells than those stably expressing full-length Zmiz1-HA, despite lacking significant differential transcript expression as analyzed by qRT-PCR (data not shown). Where indicated, MG132 (20μm) treatment increased protein stability, suggesting Zmiz1 and Zmiz1Δ1-185 are degraded by the proteasome and that stability is regulated at the protein level.

Mentions: As previously mentioned, transposon insertions in our SB screen clustered in intron 8 of Zmiz1, demonstrating a strong preference for a transcript mimicking ZMIZ1short rather than full-length ZMIZ1. In an attempt to explain why the short-form might give tumor cells a selective advantage, we examined steady-state protein expression levels of full-length and truncated Zmiz1 expressed from recombinant retroviruses in multiple cell lines (Figure 4). Higher steady-state expression of Zmiz1Δ1-185 was consistently observed across independent cell lines, despite no significant differences in transcript levels as assessed by qRT-PCR (data not shown). This suggests that Zmiz1 protein stability is regulated. Consistent with this hypothesis, Zmiz1 protein stability was increased upon treatment with the proteasomal inhibitor MG132 (Figure 4). This result indicates that increased protein stability might confer a selective advantage to tumor cells expressing Zmiz1Δ1-185 during tumorigenesis.


Ectopic expression of Zmiz1 induces cutaneous squamous cell malignancies in a mouse model of cancer.

Rogers LM, Riordan JD, Swick BL, Meyerholz DK, Dupuy AJ - J. Invest. Dermatol. (2013)

Zmiz1Δ1-185 displays increased protein stabilityWestern blots show higher steady-state protein expression in Zmiz1Δ1-185-HA-expressing HeLa, MCF7, and N-HSK-1 cells than those stably expressing full-length Zmiz1-HA, despite lacking significant differential transcript expression as analyzed by qRT-PCR (data not shown). Where indicated, MG132 (20μm) treatment increased protein stability, suggesting Zmiz1 and Zmiz1Δ1-185 are degraded by the proteasome and that stability is regulated at the protein level.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3672356&req=5

Figure 4: Zmiz1Δ1-185 displays increased protein stabilityWestern blots show higher steady-state protein expression in Zmiz1Δ1-185-HA-expressing HeLa, MCF7, and N-HSK-1 cells than those stably expressing full-length Zmiz1-HA, despite lacking significant differential transcript expression as analyzed by qRT-PCR (data not shown). Where indicated, MG132 (20μm) treatment increased protein stability, suggesting Zmiz1 and Zmiz1Δ1-185 are degraded by the proteasome and that stability is regulated at the protein level.
Mentions: As previously mentioned, transposon insertions in our SB screen clustered in intron 8 of Zmiz1, demonstrating a strong preference for a transcript mimicking ZMIZ1short rather than full-length ZMIZ1. In an attempt to explain why the short-form might give tumor cells a selective advantage, we examined steady-state protein expression levels of full-length and truncated Zmiz1 expressed from recombinant retroviruses in multiple cell lines (Figure 4). Higher steady-state expression of Zmiz1Δ1-185 was consistently observed across independent cell lines, despite no significant differences in transcript levels as assessed by qRT-PCR (data not shown). This suggests that Zmiz1 protein stability is regulated. Consistent with this hypothesis, Zmiz1 protein stability was increased upon treatment with the proteasomal inhibitor MG132 (Figure 4). This result indicates that increased protein stability might confer a selective advantage to tumor cells expressing Zmiz1Δ1-185 during tumorigenesis.

Bottom Line: Here we show that transposon-induced mutations in Zmiz1 drive expression of a truncated transcript that is similar to an alternative endogenous ZMIZ1 transcript found to be overexpressed in human SCCs relative to normal skin.In addition, we found that the alternative Zmiz1 isoform has greater protein stability than its full-length counterpart.Finally, we provide evidence that ZMIZ1 is overexpressed in a significant percentage of human breast, ovarian, and colon cancers in addition to human SCCs, suggesting that ZMIZ1 may play a broader role in epithelial cancers.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy and Cell Biology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA.

ABSTRACT
Cutaneous squamous cell carcinoma (SCC) is the second most common form of cancer in the human population, yet the underlying genetic mechanisms contributing to the disease are not well understood. We recently identified Zmiz1 as a candidate oncogene in nonmelanoma skin cancer through a transposon mutagenesis screen. Here we show that transposon-induced mutations in Zmiz1 drive expression of a truncated transcript that is similar to an alternative endogenous ZMIZ1 transcript found to be overexpressed in human SCCs relative to normal skin. We also describe an original mouse model of invasive keratoacanthoma driven by skin-specific expression of the truncated Zmiz1 transcript. Unlike most mouse models, Zmiz1-induced skin tumors develop rapidly and in the absence of promoting agents such as phorbol esters. In addition, we found that the alternative Zmiz1 isoform has greater protein stability than its full-length counterpart. Finally, we provide evidence that ZMIZ1 is overexpressed in a significant percentage of human breast, ovarian, and colon cancers in addition to human SCCs, suggesting that ZMIZ1 may play a broader role in epithelial cancers.

Show MeSH
Related in: MedlinePlus