Margarita Salas

Consejo Superior de Investigaciones Cientificas (CSIC)


Election Year: 2007
Primary Section: 26, Genetics
Secondary Section: 21, Biochemistry
Membership Type: Foreign Associate

Research Interests

As a molecular biologist, I have studied the replication and transcription mechanisms using the Bacillus subtilis bacteriophage phi29 as a model system. The phage DNA, about 19kb long, has a protein covalently linked at the two 5' ends, the so-called terminal protein (TP). Phage phi29 replication starts at both DNA ends by a mechanism in which a free molecule of the TP acts as a primer to incorporate the first nucleotide to the OH group of a specific serine residue, catalyzed by the phage DNA polymerase, giving rise to the initiation product, TP-dAMP. Then, the same DNA polymerase catalyzes elongation producing unit length phi29 DNA in a highly processive way, coupling polymerization to strand displacement. Using the phi29 TP, DNA polymerase, the double-strand DNA binding protein p5 and the single-strand DNA binding protein p6, small amounts of phi29 TP-DNA have been amplified in vitro over 1000-fold. The amplified DNA was fully infective. Because of its properties, phi29 DNA polymerase has been used as a tool for amplification of both circular and linear DNA. I have also studied the control of phi29 DNA transcription. Early genes are transcribed from several promoters recognized by the host RNA polymerase, whereas late genes are transcribed from a single promoter that requires, in addition, the phage regulatory protein p4 and the DNA binding protein p6. These two proteins are also repressors of some of the early promoters. More recently, I have also worked on the role of host proteins, among them the actin-like cytoskeleton proteins, in phi29 DNA replication.

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