A Schistosoma mansoni Pad1 homologue stabilizes c-Jun

Area of Science:

• Molecular biology
• Parasitology
• Biochemistry

Background:

• Pad1 family proteins are subunits of the 26S proteasome.
• Pad1 proteins are implicated as positive transcription modulators in yeast.
• Schistosoma mansoni is a parasitic flatworm causing schistosomiasis.

Purpose of the Study:

• To clone and functionally analyze a Pad1 homologue from Schistosoma mansoni, named SmPOH.
• To investigate the role of SmPOH in transcriptional regulation.
• To determine the effect of SmPOH on c-Jun protein stability and AP-1 activity.

Main Methods:

• Cloning and expression of recombinant SmPOH in COS7 cells.
• Immunofluorescence microscopy to determine SmPOH localization.
• Reporter gene assays to measure AP-1 transcriptional activity.
• Western blot analysis to assess c-Jun protein levels.
• In vitro degradation assays to study c-Jun protein stability.

Main Results:

• SmPOH shares high amino acid identity with yeast Pad1 and human POH1.
• Recombinant SmPOH localizes to the cytoplasm and nucleus, consistent with proteasome localization.
• Overexpression of SmPOH dose-dependently stimulates AP-1 transcriptional activity.
• SmPOH increases cellular c-Jun protein levels.
• SmPOH decreases the degradation rate of c-Jun in vitro.

Conclusions:

• SmPOH functions as a positive modulator of transcription in Schistosoma mansoni.
• SmPOH enhances AP-1 transcriptional activity by increasing the stability of c-Jun.
• This mechanism makes more c-Jun available for transactivation of AP-1-responsive genes.
• Pad1 proteins may generally modulate transcription by regulating c-Jun stability.