Maintenance of long-term transposable element activity through regulation by nonautonomous elements

Area of Science:

• Genetics
• Evolutionary Biology
• Computational Biology

Background:

• Transposable elements (TEs) are mobile DNA sequences crucial for genome evolution.
• Autonomous TEs encode transposition machinery, while nonautonomous TEs depend on them.
• Nonautonomous TEs are hypothesized to regulate TE copy numbers, but stable coexistence models were lacking.

Purpose of the Study:

• To investigate the conditions for stable coexistence between autonomous and nonautonomous retrotransposons.
• To develop a stochastic model for analyzing TE dynamics.
• To provide an analytical framework for understanding TE regulation and evolution.

Main Methods:

• Development of a stochastic mathematical model for retrotransposon dynamics.
• Derivation of analytical expressions for the stationary distribution of TE copy numbers.
• Analysis of factors influencing TE coexistence and regulation.

Main Results:

• Identified conditions enabling the stable coexistence of autonomous and nonautonomous retrotransposons.
• Demonstrated that nonautonomous elements regulate stochastic fluctuations and the copy number of autonomous elements.
• Derived an analytical expression for stationary variances as a function of average copy numbers and covariance.

Conclusions:

• Nonautonomous elements can effectively regulate autonomous elements, preventing extinction and allowing long-term coexistence.
• This regulatory mechanism provides a plausible explanation for sustained transposition activity over evolutionary timescales.
• The model supports evolutionary scenarios like the long coevolution of LINE1 and Alu elements in human ancestry.