In 2015, a virus most people had never heard of suddenly made headlines around the world. Zika virus (ZIKV), long considered a mild mosquito-borne pathogen, was linked to devastating birth defects and neurological disease, reshaping how scientists think about emerging viral threats. What made Zika especially alarming was not just its rapid spread across the Americas, but its ability to cross biological barriers once thought to be well protected, from the placenta to the developing brain. Today, Zika serves as a powerful case study in understanding how various factors, potentially including subtle changes in viral biology can have profound consequences for human health—and why sustained investment in basic virology remains essential even after the headlines fade.
Against this backdrop, former graduate student Alex Willcox from Dr. Julie Overbaugh’s lab is adding a new layer to our understanding of how host cells detect and restrain Zika virus infection. Using a CRISPR knockout screen, the authors recently published a study in PNAS identifying angiomotin-like protein 2 (AMOTL2) as a previously unrecognized antiviral factor that strengthens type I interferon signaling.
“To identify antiviral genes that protect cells from Zika virus infection, we were excited to discover that AMOTL2, a gene with no previously described antiviral function, contributes to type I interferon restriction of Zika,” says Willcox. “Surprisingly, AMOTL2 isn’t a downstream product of interferon, but appears to modulate the strength of the interferon signaling pathway itself, increasing the transcription of interferon-stimulated genes that act as direct antiviral effectors. This suggests AMOTL2 is likely broadly antiviral, beyond just Zika or flaviviruses.”
To model ZIKV-induced cell death, Willcox used A549 cells—a human lung cancer cell line that undergoes apoptosis following ZIKV replication—to screen for host genes that limit viral infection. The team introduced a CRISPR library designed to knock out nearly 2,000 genes linked to interferon responses, the body’s early warning system that activates a broad network of protective genes. By looking for genes whose loss made interferon-treated cells more vulnerable to Zika-induced death, they pinpointed critical host factors that keep the virus in check
Their screen confirmed that most interferon-responsive genes, including key signaling proteins STAT1 and STAT2, were well represented in the library, alongside many genes not directly induced by interferon. This broad coverage uncovered both established antiviral genes and surprising new players influencing interferon’s effectiveness against Zika.
To validate their findings, the authors focused on six top candidate genes by knocking them out individually and testing how interferon suppression of Zika was affected. Knocking out IRF9 abolished interferon’s antiviral effect, while loss of AMOTL2 and IFI6 significantly increased viral replication under interferon treatment, highlighting their important roles. Other genes showed modest or minimal effects.
AMOTL2, traditionally known for regulating cell shape, growth, and movement—especially in blood vessel development and cancer—showed a surprising new role in antiviral defense. Knocking out AMOTL2 increased Zika replication only in interferon-treated cells, confirming that its antiviral role depends on the interferon response. Yet, unlike typical interferon-stimulated genes, AMOTL2 expression remained steady regardless of interferon exposure.
This paradox led the authors to discover that loss of AMOTL2 reduced the interferon-driven activation of multiple antiviral genes, suggesting that AMOTL2 acts by boosting the interferon signaling pathway itself rather than as a downstream effector. “We showed that inactivation of AMOTL2 causes higher levels of unphosphorylated STAT1 at baseline, correlating with reduced STAT1 activation after interferon stimulation,” explains Willcox. “We also found the coiled-coil domain of AMOTL2 is important for its antiviral function, raising new questions about how AMOTL2 modulates STAT1 and whether related proteins like AMOT and AMOTL1 have similar roles.”
The team also explored whether AMOTL2’s known interactions with the transcriptional regulators YAP and TAZ—proteins implicated in suppressing innate immunity—explain its antiviral effect. While knocking out YAP had little impact, TAZ loss actually reduced Zika infection under interferon treatment, suggesting TAZ might support viral replication. Importantly, disrupting AMOTL2’s ability to bind TAZ did not impair its antiviral activity, but deletion of AMOTL2’s coiled-coil domain abolished its function, highlighting this region as essential.
Further, AMOTL2 knockout increased infection by Sindbis virus in interferon-treated cells, demonstrating its broader role in interferon-dependent antiviral defense beyond Zika.
Looking ahead, Willcox hopes these findings inspire further study: “It will be important to confirm AMOTL2’s broad antiviral activity and understand the molecular details of its interaction with STAT1. We’re also curious whether this function extends to primary human cells and animal models. Although I’m currently back in medical school, I hope our paper motivates others to build on this work and better characterize AMOTL2’s role in antiviral immunity.”
The spotlighted research was funded by the National Institutes of Health.
Willcox AC, Gobillot TA, Kikawa C, Baumgarten NE, Stoddard CI, Sung K, Bhattacharya T, Freeman TS, Marceau J, Humes D, Overbaugh J. 2025. Identification of AMOTL2 as an antiviral factor that enhances the human type I interferon response against Zika virus. Proc Natl Acad Sci USA. DOI: 10.1073/pnas.2507955122.
Science Spotlight writer Jenny Waters is a postdoctoral research fellow in the Hsieh lab at Fred Hutch. She studies how mRNA translation coordinates bladder cancer transformation and metastasis by post-transcriptionally regulating expression of oncogenic proteins. Outside of the lab, Jenny enjoys spending time with her dogs, convincing her husband to join her on trail runs, and pretending every steep hill is just a "gentle incline."
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