RNA targeting methods and compositions

A method of targeting one or more target RNA molecules, comprising:

• contacting one or more target RNA molecules with a non-naturally occurring or engineered clustered regularly interspaced short palindromic repeats (CRISPR)-associated (Cas) system comprising:
• at least one Cas13d protein comprising at least 95% sequence identity to SEQ ID NO:
• 189, or a nucleic acid molecule encoding the at least one Cas13d protein;
• and
• at least one CRISPR-Cas system guide RNA (gRNA) comprising one or more direct repeat (DR) sequences and one or more spacer sequences, which hybridizes with the one or more target RNA molecules, or at least one nucleic acid molecule encoding the gRNA,
• whereby the Cas13d protein forms a complex with the gRNA, wherein the gRNA directs the complex to the one or more target RNA molecules and targets the one or more target RNA molecules.