A Novel Member of the Bacterial-Archaeal Regulator Family Is a Nonspecific DNA-binding Protein and Induces Positive Supercoiling

Alessandra Napoli,Mamuka Kvaratskelia,Malcolm F White,Mosé Rossi,Maria Ciaramella

doi:10.1074/jbc.m010611200

Alessandra Napoli, Mamuka Kvaratskelia + Show 3 more

Open Access

https://doi.org/10.1074/jbc.m010611200

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Abstract

In hyperthermophilic Archaea genomic DNA is from relaxed to positively supercoiled in vivo because of the action of the enzyme reverse gyrase, and this peculiarity is believed to be related to stabilization of DNA against denaturation. We report the identification and characterization of Smj12, a novel protein of Sulfolobus solfataricus, which is homologous to members of the so-called Bacterial-Archaeal family of regulators, found in multiple copies in Eubacteria and Archaea. Whereas other members of the family are sequence-specific DNA- binding proteins and have been implicated in transcriptional regulation, Smj12 is a nonspecific DNA-binding protein that stabilizes the double helix and induces positive supercoiling. Smj12 is not abundant, suggesting that it is not a general architectural protein, but rather has a specialized function and/or localization. Smj12 is the first protein with the described features identified in Archaea and might participate in control of superhelicity during DNA transactions.

Highlights

In hyperthermophilic Archaea genomic DNA is from relaxed to positively supercoiled in vivo because of the action of the enzyme reverse gyrase, and this peculiarity is believed to be related to stabilization of DNA against denaturation
We report the identification and characterization of Smj12, a novel protein of Sulfolobus solfataricus, which is homologous to members of the socalled Bacterial-Archaeal family of regulators, found in multiple copies in Eubacteria and Archaea
We report the identification of a novel DNA-binding protein of Sulfolobus solfataricus, named Smj12, which is homologous to the transcription regulator Lrs14, an archaeal repressor belonging to the BA family; unlike Lrs14, Smj12 is a nonspecific DNA-binding protein

Summary

Introduction

In hyperthermophilic Archaea genomic DNA is from relaxed to positively supercoiled in vivo because of the action of the enzyme reverse gyrase, and this peculiarity is believed to be related to stabilization of DNA against denaturation. Whereas other members of the family are sequence-specific DNAbinding proteins and have been implicated in transcriptional regulation, Smj12 is a nonspecific DNA-binding protein that stabilizes the double helix and induces positive supercoiling. By using topoisomerase I assays we show that Smj12 induces positive supercoiling of minicircle and plasmid DNA.

Results

Conclusion