t-RNAs and protein degradation

[Donald Chen - Microbiology]

Hi:

I've just come across two papers which discuss eukaryotic
degradation via ubiquitin.  These are by Ciechanover et al
PNAS 82:1341-1345 (1985) and Ferber and Ciechanover
Nature 326:808-811 (1987).  Both papers show that charged t-RNA (arg)
is necessary for protein degradation via the ubiquitin pathway.
I have some questions for those who might be in this field of
research.

1.  Have any of the authors continued to look into the role of
	t-RNA in ubiquitin mediated proteolysis?
2.  Is there in vivo evidence of t-RNA charging of cellular
	proteins which are destined for degradation?
3.  Is there a prokaryotic version of t-RNA and proteolysis?
	Yes, I know that there is no evidence of an ubiquitin-like
	molecule in prokaryotes.  But do t-RNAs have any role
	in prokaryotic proteolysis?
4.  I have learned that t-RNAs may have a role in transcription
	by RNA pol III.  Are there other roles for t-RNAs other than
	translation in either eukaryotes or prokaryotes?
5.  If t-RNAs are involved in marking/facilitating ubiquitin
	mediated proteolysis where are these t-RNAs coming from-
	the nucleus? Does ubiquitin work in the nucleus as well as
	the cytoplasm?

Any help would greatly be appreciated.

Don Chen
Oregon State Univ
Dept of Microbiology