Tetrahymena micronuclear sequences that function as telomeres in yeast

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• Telomeres protect chromosome ends from degradation and fusion.
• The sequence and structure of telomeric repeats are critical for telomere function.
• Investigating heterologous telomere utilization provides insights into conserved mechanisms.

Purpose of the Study:

• To determine if Saccharomyces cerevisiae (yeast) can use DNA sequences from Tetrahymena thermophila as functional telomeres.
• To identify specific Tetrahymena DNA sequences that confer telomere function in yeast.
• To explore the ability of yeast to heal broken chromosome ends using internal telomere-like sequences.

Main Methods:

• Cloning of germline DNA from Tetrahymena thermophila into a linear yeast plasmid designed to select for telomere function.
• Assaying the ability of cloned Tetrahymena DNA fragments to stabilize the linear plasmid in yeast.
• Analyzing the sequence and location of functional Tetrahymena DNA elements within the yeast plasmid.

Main Results:

• Only the (C4A2)n repeat sequences from Tetrahymena functioned as telomeres in yeast.
• These (C4A2)n repeats did not need to originate from Tetrahymena telomeres; internal chromosomal fragments also worked.
• Yeast elongated the functional Tetrahymena (C4A2)n repeats with its own telomeric sequences, and stabilized linear plasmids.

Conclusions:

• Saccharomyces cerevisiae can recognize and utilize specific heterologous DNA sequences, namely (C4A2)n repeats, as functional telomeres.
• The yeast system demonstrates broken chromosome healing by utilizing internally located telomere-like sequences.
• This study highlights the importance of the telomeric repeat structure for in vivo recognition and function.