What are piRNA and tiRNA ?

[A. Hammouda]

What are piRNA and tiRNA?

and how are they related to other RNAs?

[W. Norman]

Piwi-interacting RNAs (piRNAs) and tRNA-derived small RNAs (tiRNAs) are both types of small non-coding RNAs involved in various cellular processes, particularly in the regulation of gene expression and maintenance of genome integrity.

piRNAs are a class of small non-coding RNAs, typically 24-31 nucleotides long, that interact with Piwi proteins. They are primarily expressed in the germline cells, where they play crucial roles in silencing transposable elements (TEs).

See this: https://bioinformaticshub.net/forums/topic/what-are-transposons-transposases-and-transposomes/

piRNAs guide Piwi proteins to complementary sequences in TEs, leading to their silencing through various mechanisms, including DNA methylation and heterochromatin formation.

Besides their role in TE silencing, piRNAs have also been implicated in other processes such as epigenetic regulation, germ cell development, and possibly even in diseases like cancer.

tiRNAs are small RNAs derived from transfer RNAs (tRNAs), They are generated through the cleavage of mature tRNAs under various stress conditions, such as nutrient deprivation, heat shock, or oxidative stress.

These small RNAs, typically around 18-22 nucleotides long, have been shown to regulate gene expression by targeting mRNAs and affecting translation. tiRNAs can function through multiple mechanisms, including inhibition of translation initiation, modulation of ribosome dynamics, and possibly by serving as competitive inhibitors of microRNAs (miRNAs) or other RNA-binding proteins.

Although their exact biological functions are still being elucidated, tiRNAs have been implicated in stress responses, development, and diseases such as cancer.

In summary, piRNAs and tiRNAs are both small non-coding RNAs that play important roles in gene regulation and cellular homeostasis, with piRNAs primarily involved in silencing transposable elements in germline cells, while tiRNAs are implicated in stress responses and translational regulation.

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