cDNA cloning, recombinant expression and characterization of polypetides with exceptional DNA affinity

Area of Science:

• Molecular Biology
• Genomics
• Biochemistry

Background:

• Polypeptides tightly associated with genomic DNA are implicated in DNA topology and function.
• Investigating these residual DNA-polypeptide complexes is crucial for understanding genome organization.

Purpose of the Study:

• To identify and characterize polypeptides that remain associated with isolated genomic DNA.
• To clone the cDNA encoding such a polypeptide and investigate its properties.

Main Methods:

• Generation of monoclonal antibodies against DNA-polypeptide complexes.
• Screening a murine lambda gt11 cDNA library using these antibodies.
• Sequencing of homologous human cDNA (HC1D) and recombinant protein expression.
• Western blot analysis and immunofluorescence staining using polyclonal antiserum.

Main Results:

• A cDNA (MC1D) encoding a 16 kDa polypeptide was isolated.
• The human homolog (HC1D) was identified and sequenced; its protein product contains nuclear localization signals but lacks known DNA-binding motifs.
• Recombinant proteins demonstrated in vitro DNA-binding affinities.
• Antiserum detected the 16 kDa polypeptide in DNA digests and stained sub-nuclear structures.

Conclusions:

• The cloned cDNAs encode a chemically-resistant 16 kDa polypeptide associated with genomic DNA.
• This polypeptide likely plays a role in the structural organization or function of genomic DNA.
• The findings contribute to understanding the proteins that interact with and maintain the integrity of the genome.