PT  - JOURNAL ARTICLE
AU  - Bonita H. Powell
AU  - Andrey Turchinovich
AU  - Yongchun Wang
AU  - Zhaohao Liao
AU  - Mohammad Aasif Dar
AU  - Gaspare La Rocca
AU  - George Essien Umanah
AU  - Martha A. Zeiger
AU  - Christopher B. Umbricht
AU  - Kenneth W. Witwer
TI  - mir-21 is associated with inactive low molecular weight Argonaute complexes in thyroid cancer cell lines
AID  - 10.1101/2020.03.24.006072
DP  - 2020 Jan 01
TA  - bioRxiv
PG  - 2020.03.24.006072
4099  - http://biorxiv.org/content/early/2020/03/26/2020.03.24.006072.short
4100  - http://biorxiv.org/content/early/2020/03/26/2020.03.24.006072.full
AB  - Thyroid cancer is the most prevalent malignancy of the endocrine system. We and others have shown that several microRNAs, which are post-transcriptional gene regulators, are aberrantly expressed in anaplastic thyroid cancer (ATC) and papillary thyroid cancer (PTC) tissues, as well as cell lines derived from these cancers. In the cell, miRNAs are bound to Argonaute (AGO) proteins as what could be termed low molecular weight RNA-Induced Silencing Complexes (LMW-RISCs) that can then assemble with additional proteins, mRNA, and translation machinery into high molecular weight RISCs (HMW-RISCs) that also exert regulatory function. In this study, we sought to analyze the association of miRNAs with RISC complexes in ATC and PTC. For ATC and PTC lines, miRNA species were enriched in both HMW-RISC and LMW-RISC cellular fractions, compared with intermediate molecular weight fractions and very low molecular weight (AGO-poor) fractions. Furthermore, 60% of all miRNAs were slightly more abundant in LMW-RISC versus HMW-RISC fractions by ∼2-4 fold. Surprisingly, miR-21-5p, one of the most abundant miRNAs in both ATC and PTC lines and one of the most widely studied oncogenic miRNAs in many solid tumors, was consistently one the least abundant miRNAs in HMW-RISC and the most enriched miRNA in LMW-RISC fractions. These findings may suggest that miR-21 has a role or roles distinct from canonical posttranscriptional regulation in cancer. Furthermore, the methodology described here is a useful way to assess the distribution of miR-21 between HMW and LMW-RISCs and may help to reveal the true roles of this miRNA in thyroid cancer development, progression, and treatment.