Alternative transcription increases isoform complexity in Long Non-Coding RNAs and alters their functions in cancer

Transcriptional start and end variance, a less-explored aspect of lncRNA biology, is a critical determinant of isoform diversity in human RNA. While alternative splicing (AS) has been extensively studied as a mechanism of isoform generation, differences in transcriptional start and termination site usage-whether from distinct promoters or varying initiation events at the same core promoter-contribute more to isoform diversity than alternative splicing. In the context of long non-coding RNAs (lncRNAs), even subtle alterations to transcriptional start and end sites can induce significant changes in the structural and functional capacities of individual lncRNA isoforms. This review highlights the underappreciated realm of transcriptional start and end variance in lncRNAs, exploring its pivotal role in shaping the diversity of lncRNA transcripts. In cancer, where lncRNAs are increasingly recognised as key players in tumorigenesis, understanding the ramifications of transcriptional start and end variance is crucial. With single nucleotide alterations capable of influencing the folding energy, shape, stability, and function of a lncRNA molecules, significant changes to transcriptional regulation may lead to aberrant isoforms with implications for cancer initiation, progression, and potentially, its treatment. As lncRNAs emerge as therapeutic targets, particularly with the advancement of antisense oligonucleotide (ASO) technologies, it becomes crucial to understand the regulatory landscape of transcriptional variation among lncRNA isoforms, to ensure selective targeting of oncogenic transcripts while sparing those with normal physiological functions. By highlighting the significance of transcriptional start and end site variation as major contributors to lncRNA diversity, the potential exploitation for precision therapeutic interventions in the field of non-coding RNA cancer research can be expanded.