# Molecular Characteristics, Circularization Mechanism, and Potential Functions of circRNA-0172

## TL;DR

This study identifies a circular RNA (circRNA-0172) that is involved in the response to ALV-J infection in poultry and may help control avian leukemia.

## Contribution

The study is the first to confirm circRNA-0172's stability and its repeat-dependent circularization mechanism in ALV-J infection.

## Key findings

- circRNA-0172 is cytoplasm-localized, RNase R-resistant, and circularized via ERVL-MaLR repeats.
- Overexpression of circRNA-0172 inhibits DF-1 cell proliferation and alters apoptosis-related gene expression.
- circRNA-0172 is downregulated by ALV-J infection and is highly expressed in immune tissues.

## Abstract

Background/Objectives: Avian leukosis virus subgroup J (ALV-J) harms poultry via tumors and immunosuppression; MDM2-derived circRNA-0172′s role in ALV-J infection is unknown. This study explores its molecular characteristics, circularization mechanism and functions for ALV-J control. Methods: CEF/DF-1/HD11 cells were cultured; RNA/DNA was extracted. circRNA-0172 was validated via PCR, sequencing and RNase R; subcellular localization and circularization were analyzed with fractionation and vectors. miRanda/TargetScan/GO/KEGG, CCK-8 and qRT-PCR assessed targets, pathways and functions. Results: circRNA-0172 (1180 bp, MDM2 exons 3–11) is cytoplasm localized, RNase R resistant, and circularized via flanking ERVL-MaLR repeats. Highly expressed in immune tissues/HD11 cells, it is downregulated by ALV-J. Its overexpression inhibits DF-1 proliferation, downregulates Bcl2 and upregulates CCND1. Conclusions: This is the first confirmation of circRNA-0172′s stability and repeat-dependent circularization; it regulates cell proliferation/apoptosis, providing potential targets for ALV-J-associated avian leukemia.