Details

Autor(en) / Beteiligte

• Conte, Emanuele
• Vincelli, Gabriele
• Schaaper, Roel M
• Bressanin, Daniela
• Stefan, Alessandra
• Piaz, Fabrizio Dal
• Hochkoeppler, Alejandro

Titel

Stabilization of the Escherichia coli DNA polymerase III Im subunit by the I, subunit favors in vivo assembly of the Pol III catalytic core

Ist Teil von

• Archives of biochemistry and biophysics, 2012-07, Vol.523 (2), p.135-143

Erscheinungsjahr

2012

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Escherichia coli DNA polymerase III holoenzyme (HE) contains a core polymerase consisting of three subunits: I- (polymerase), Im (3a2-5a2 exonuclease), and I,. Genetic experiments suggested that I, subunit stabilizes the intrinsically labile Im subunit and, furthermore, that I, might affect the cellular amounts of Pol III core and HE. Here, we provide biochemical evidence supporting this model by analyzing the amounts of the relevant proteins. First, we show that a IholE strain (lacking I, subunit) displays reduced amounts of free Im. We also demonstrate the existence of a dimer of Im, which may be involved in the stabilization of the protein. Second, I,, when overexpressed, dissociates the Im dimer and significantly increases the amount of Pol III core. The stability of Im also depends on cellular chaperones, including DnaK. Here, we report that: (i) temperature shift-up of IdnaK strains leads to rapid depletion of Im, and (ii) overproduction of I, overcomes both the depletion of Im and the temperature sensitivity of the strain. Overall, our data suggest that Im is a critical factor in the assembly of Pol III core, and that this is role is strongly influenced by the I, subunit through its prevention of Im degradation.