CRISPR/Cas13 effectors have garnered increasing attention as easily customizable tools for detecting and depleting RNAs of interest but have been debated for the potential for off-target effect. In Part I of this thesis, using co-transfection assays in Drosophila and human cells, we found that the off-target effects of RxCas13d can be as strong as the level of on-target RNA knockdown and the extent of off-target effects is positively correlated with target RNA expression levels. The PspCas13b effector showed improved specificity and, unlike RxCas13d, can be used to deplete a Drosophila circular RNA without affecting the expression of the associated linear RNA. PspCas13b nonetheless still can have off-target effects and we notably found that the extent of off-target effects for Cas13 effectors differs depending on the cell type and target RNA examined. In total, these results highlight the need for caution when designing and interpreting Cas13-based knockdown experiments.Alternative polyadenylation (APA) of pre-mRNA generates 3’ end isoforms with different lengths of the 3’ untranslated region (3’ UTR). APA is often dysregulated in cancer, but the understanding of the functional consequences of APA isoform changes is limited. In Part II of this thesis, we have identified, through transcriptome-wide analysis, a significantly regulated APA isoform event of the gene encoding tissue inhibitor of metalloproteinase 2 (Timp2) in mouse fibroblast cell NIH3T3 transformed by the oncogene HRASG12V. Timp2 expresses short and long APA isoforms that differ in a sizable (~2.5 kb) alternative 3’UTR (aUTR). By generating Timp2 aUTR knockdown and heterozygous knockout cells, we find that the long isoform is the major contributor to the abundance of secreted Timp2 protein. Through high-throughput sequencing, we find hundreds of genes in HRASG12V transformed cells that are potentially regulated through Timp2 shortening and, consistently, knockdown of Timp2 long isoform mitigates gene expression changes elicited by HRASG12V. We also explore the subcellular localization difference between the isoforms. Overall, we have uncovered aspects of functional significance of Timp2 aUTR in mRNA metabolism and protein production.