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Related Experiment Video

Updated: Jun 11, 2025

Functional Imaging of Viral Transcription Factories Using 3D Fluorescence Microscopy

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Published on: January 18, 2018

KSHV ORF20 Promotes Coordinated Lytic Reactivation for Increased Infectious Particle Production.

Odelia Orbaum-Harel^1,2, Anna Sloutskin¹, Inna Kalt^1,2

¹The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat Gan 5290002, Israel.

|September 28, 2024

Summary

This summary is machine-generated.

Kaposi's sarcoma-associated herpesvirus open reading frame 20 (ORF20) protein promotes viral replication and infectious particle production. Its endonuclease activity is crucial for efficient KSHV lytic reactivation and coordinated viral gene expression.

Keywords:

KSHV Kaposi’s sarcoma-associated herpesvirus ORF20 UL24 lytic reactivation open reading frame 20 unique long 24

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Published on: August 25, 2017

Area of Science:

Virology
Molecular Biology
Oncology

Background:

Kaposi's sarcoma-associated herpesvirus (KSHV) causes lifelong infections and is linked to cancers like Kaposi's sarcoma.
KSHV open reading frame 20 (ORF20) belongs to the conserved herpesvirus UL24 protein family and possesses a putative endonuclease motif.
The specific functions of ORF20 and its isoforms during KSHV infection remain largely uncharacterized.

Purpose of the Study:

To investigate the role of KSHV ORF20 in viral infection and replication.
To determine the functional significance of ORF20's putative endonuclease activity.
To elucidate the impact of ORF20 on viral lytic reactivation and gene expression.

Main Methods:

Generation of a recombinant ORF20-Null KSHV genome.
Reconstitution of the KSHV genome in iSLK cells to establish latent infection.
Functional complementation assays using ORF20 isoforms and an endonuclease mutant.

Main Results:

ORF20-Null KSHV infection led to accelerated viral mRNA transcription, earlier lytic protein accumulation, and increased viral DNA copies.
A significant decrease in viral yield and increased cell death were observed in ORF20-Null infected cells upon reactivation.
Complementation with the short ORF20 isoform rescued KSHV production and reduced cell death, while the endonuclease mutant failed to enhance lytic reactivation.
Expression of IL6 and CXCL8 was reduced in ORF20-Null infected cells.

Conclusions:

KSHV ORF20 protein, particularly its endonuclease motif, is essential for promoting coordinated lytic reactivation.
ORF20 facilitates efficient infectious particle production and regulates viral gene expression, including IL6 and CXCL8.
The short ORF20 isoform is sufficient to rescue KSHV production and mitigate ORF20-null associated cell death.