Interactions of human replication protein A with oligonucleotides

Area of Science:

• Molecular Biology
• Biochemistry
• Genetics

Background:

• Replication protein A (RPA) is a vital heterotrimeric protein complex essential for eukaryotic DNA replication.
• Understanding RPA's interaction with single-stranded DNA is critical for elucidating DNA replication mechanisms.

Purpose of the Study:

• To investigate the binding characteristics of human RPA to single-stranded DNA oligonucleotides.
• To determine the binding site size, stoichiometry, and affinity of human RPA for DNA.

Main Methods:

• Analysis of RPA-DNA complexes using stoichiometric binding reactions.
• Monitoring DNA binding through fluorescence quenching assays.
• Systematic examination of RPA binding to deoxythymidine-containing oligonucleotides of varying lengths.

Main Results:

• Human RPA binds to single-stranded DNA as a heterotrimer.
• The binding site size of human RPA is 30 nucleotides, with 20-30 nucleotides directly interacting with the protein.
• RPA binding affinity is length-dependent, with apparent association constants ranging from 7 x 10^7 M^-1 for oligo(dT)10 to 1.5 x 10^10 M^-1 for oligo(dT)50.
• Human RPA exhibits low cooperativity in DNA binding, with a cooperativity parameter (omega) of approximately 15.

Conclusions:

• Human RPA functions as a heterotrimer in binding single-stranded DNA.
• The binding affinity and site size of RPA are precisely defined and dependent on DNA length.
• These findings provide crucial insights into the molecular interactions governing DNA replication and repair processes.