Description

The PCIF1 Knockout MDCK Cell Line is a CRISPR/Cas9-edited canine epithelial cell model featuring disruption of the PCIF1 (phosphorylated CTD-interacting factor 1) gene. PCIF1 encodes a cap-specific adenosine N6-methyltransferase that catalyzes the formation of N6,2??-O-dimethyladenosine (m6Am) at the transcription start nucleotide of capped mRNAs. This knockout cell line provides a defined loss-of-function system to dissect the regulatory roles of the m6Am modification in mRNA metabolism without altering other cap methyltransferases.

The parental MDCK cell line is derived from normal canine kidney epithelium, retaining key characteristics of polarized epithelial monolayers, including tight junction formation, vectorial ion transport, and fluid absorption. As a non-tumorigenic line, MDCK cells are a gold-standard model for investigating epithelial cell polarity, barrier function, and membrane trafficking. Their wide use in influenza virus propagation and antiviral research further expands the utility of this knockout system for host?Cpathogen interaction studies.

Mechanistically, PCIF1 is recruited to actively transcribing RNA polymerase II (Pol II) through an interaction with the Ser5-phosphorylated C-terminal domain (CTD) of the largest Pol II subunit, a process facilitated by the transcription elongation factors SPT5 and the PAF1 complex. PCIF1 then methylates the N6 position of the cap-adjacent adenosine, generating m6Am on nascent transcripts. This modification can either stabilize or destabilize target mRNAs, such as EGR1, JUN, and FOS, and generally enhances translation initiation via improved binding of eIF4E. Upstream, PCIF1 activity is regulated by the CDK9?CP-TEFb kinase complex, which phosphorylates Pol II CTD at Ser5, and by the cap methyltransferase RNMT that generates the m7G cap, a prerequisite for PCIF1 action.

In the context of MDCK epithelium, PCIF1-mediated m6Am deposition is poised to play a critical role in maintaining the polarity program and tight junction integrity. Epithelial cells rely on precise spatiotemporal control of mRNA turnover and localized translation to maintain apicobasal polarity and respond to extracellular cues. Disruption of PCIF1 in this model allows investigation of how m6Am-dependent post-transcriptional regulation influences junctional protein expression, epithelial barrier formation (as measured by transepithelial electrical resistance, TEER), and the structural organization of tight junctions. Furthermore, the line is valuable for exploring the contribution of m6Am to viral replication, particularly for influenza viruses that depend on host cap structures for their own mRNA synthesis.

This knockout cell line is suited for a range of experimental workflows to probe m6Am biology. Users can validate PCIF1 depletion by western blotting and assess global m6Am levels via dot blot or LC-MS/MS. Transcript-specific effects can be examined using actinomycin D chase assays to measure mRNA half-lives of targets like EGR1 or JUN, combined with polysome profiling to monitor translation efficiency. The epithelial nature of MDCK cells permits immunofluorescence localization of tight junction markers (e.g., ZO-1, occludin) and functional barrier assays such as TEER measurements. Additionally, the line can be employed in influenza A replication assays to study host methylation factors in viral propagation. For any inquiries regarding this product or related services, please contact Ascent Research.