Dear All,
I would like to ask you if you have tried or if you have come across a paper showing the effects of elevated 26S proteasome activity on protein ubiquitination by immunoblotting analysis using an anti-Ub antibody. Similarly to the proteasome inhibition by MG132, where the presence of ubiquitinated proteins increases on the immunoblot, should I expect a decreased signal of ubiquitinated proteins when the proteasome activity is promoted? Any suggestions would be very helpful.
Many thanks,
Olga
Hi Olga,
[The answer is NO]
What I believe (and observed from my experiments);
If you inhibit Proteasome activity by MG132, you see elevation of ubiquitination by WB; because ubiquitinated proteins get accumulated...!!! This is a straight forward effect.
But If you increase Proteasome activity you may not see decreased ubiquitination. From my experience (In one of my paper-FEBSJ), I increased proteasome activity by overexpressing one of the 19S subunit but did not observe any decrease ubiquitination. Increased proteasome activity does not mean that it will degrade the ubiquitinated proteins faster and show up less in immunobloting experiment. When Ub-ligase activity decreases you may see this effect..!!
Cancer cells very often exhibit high Proteasome activity and do not show less ubiquitination. Its actually the balance between the two process.
"So you should not expect a decreased signal of ubiquitination pattern when the proteasome activity is promoted."
I hope this will help you.
Good Luck.
Hi Indrajit,
That was very helpful! Thank you for your comment.
Best regards,
Olga
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