Evidence for GroES acting as a transcriptional regulator.
Cochaperonins (cpn10) assist chaperonins (cpn60) in promoting folding and assembly of other proteins. Upon expression of Mycobacterium tuberculosis cpn10 in Escherichia coli we have purified a polypeptide which, through amino acid sequencing, was identified as the endogenous E. coli 10K-S protein. Subsequent studies showed that its expression was specifically upregulated upon cloning of different members of the cpn10 family, including GroES, the E. coli cpn10. Pulse-chase experiments demonstrated that 10K-S is but one of several proteins whose expression is modulated upon cloning of cpn10. Up-regulation of 10K-S was also observed after exposure of normal cells, but not of groES- mutants, to elevated temperatures (42 degrees C). This allowed us to define 10K-S as a heat-shock protein (hsp) whose expression is dependent on the production of another hsp, GroES. Northern blot experiments showed that enhanced expression of 10K-S was consequent to increased accumulation of transcripts and that groES- mutants were devoid even of baseline levels of transcripts both at 37 degrees C and after temperature upshift. These results show that GroES, in addition to its established role in assisting protein folding may act as a transcriptional regulator and is likely to play an important role in modulating gene expression particularly in those conditions, like the stress response, in which its production is greatly enhanced.
Legname
G
G
Centro Ricerche Italfarmaco S.p.A., Milan, Italy.
Buono
P
P
Fossati
G
G
Monzini
N
N
Mascagni
P
P
Modena
D
D
Marcucci
F
F
D000595:Amino Acid Sequence; D018835:Chaperonin 10 / Q000235:genetics / Q000502:physiology*; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D008969:Molecular Sequence Data; D009169:Mycobacterium tuberculosis / Q000235:genetics; D014158:Transcription, Genetic / Q000502:physiology*
D018835:Chaperonin 10