Lack of positional requirements for autonomously replicating sequence elements on artificial yeast chromosomes

Area of Science:

• Molecular Biology
• Genetics
• Yeast Biology

Background:

• Eukaryotic chromosome architecture can be studied using artificial chromosomes in yeast.
• Origins of replication (autonomously replicating sequences; ARSs), centromeres, and telomeres are key chromosomal elements.
• Natural yeast chromosomes often feature ARSs near their ends.

Purpose of the Study:

• Investigate the role of telomeric ARSs in artificial chromosome maintenance.
• Determine the necessity of ARSs on chromosomal arms for stability.
• Analyze the impact of ARS-free arms on chromosome stability.

Main Methods:

• Construction and introduction of artificial chromosomes (15 and 60 kb) into yeast.
• Analysis of telomeric ARS requirements and ARS-free arm effects.
• Assessment of chromosome stability during mitosis and meiosis.

Main Results:

• Terminal telomeric repeat blocks are sufficient for telomere recognition.
• Artificial chromosomes with telomeric ARSs were not more stable than those without.
• Yeast telomeric sequences are the sole cis-acting requirement for functional telomeres.
• No ARS is required on each arm for chromosome stability.

Conclusions:

• Functional telomeres in yeast are established by telomeric sequences alone.
• Origins of replication are not essential on each arm of artificial chromosomes.
• Replication forks can efficiently traverse functional centromere regions.