Question 5: Methodology for Distinguishing lncRNA Functional Modes In the study of lung cancer vulnerabilities, Esposito et al. (2022) noted that genomic deletion (CRISPR-del) of a lncRNA locus cannot distinguish between a DNA-dependent (e.g., an enhancer element) or an RNA-dependent (the transcript itself) mechanism. Task: Apply the methodology found in the paper to a hypothetical scenario: If you have a screen hit at the candidate 205 (LINC00115) locus, describe how you would use Antisense Oligonucleotides (ASOs) to prove that the oncogenic phenotype is mediated by the RNA transcript rather than the underlying DNA sequence.

What is the main limitation of genomic deletion (CRISPR-del) for studying lncRNA loci?

It cannot distinguish between a DNA-dependent mechanism (e.g., enhancer element) and an RNA-dependent mechanism (the transcript itself).

Why does CRISPR-del create ambiguity about the mechanism of a lncRNA locus?

Because the observed phenotype could result from loss of a cis-regulatory DNA element (like an enhancer) rather than loss of the RNA transcript.

What additional complication exists at the candidate 205 (LINC00115) locus?

The locus is bidirectional, overlapping two genes (LINC00115 and RP11-206L10.11), so DNA deletion alone cannot distinguish which gene or the DNA sequence itself is functional.

How do Antisense Oligonucleotides (ASOs) work?

They bind to and induce degradation of the mature RNA transcript without altering the genomic DNA sequence.

What is the key advantage of ASOs over CRISPR-del for proving RNA-dependent mechanisms?

ASOs target the RNA transcript directly while leaving the genomic DNA sequence unchanged.

What would you do first to test if LINC00115 mediates its oncogenic phenotype via the RNA transcript?

Design and transfect cells with independent ASO sequences specifically targeting the LINC00115 transcript.

What functional assays would you perform after ASO-mediated knockdown?

Cell proliferation or competition assays to measure oncogenic suppression.

If ASO knockdown of LINC00115 recapitulates the reduced growth seen with CRISPR-del, what does that prove?

That the phenotype is RNA-dependent (mediated by the transcript itself).

If ASO knockdown of LINC00115 has no effect despite successful knockdown, what does that indicate?

The original CRISPR-del hit was likely a false positive acting through a DNA-dependent mechanism, such as an overlapping enhancer.

How did Esposito et al. (2022) use this methodology?

To confirm that LINC00115, and not its neighboring gene, was the functional driver of cell proliferation via an RNA-dependent mechani