Cytoplasmic mRNAs are degraded by one of the three pathways. For most mRNAs, the deadenylation-dependent pathway is followed These dense regions of cytoplasm contain the decapping enzyme (DCP1/DCP2), activators of decapping (DHH, PAT1, LSM1-7), and the major 5′→3′ exoribonuclease XRN1, as well as densely associated mRNAs

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#Unit 3. Fundamental Processes

The estimate is that as much as 70% of human genes produce antisense RNA.

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#Unit 3. Fundamental Processes

Clustered Regularly Interspaced Short Palindromic Repeats CRISPR consist of repeated sequences (each 30 bp long and highly conserved within a given cluster) interleaved with spacer sequences of similar length but highly divergent sequence.

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#Unit 3. Fundamental Processes

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#Unit 3. Fundamental Processes

A set of conserved protein-coding genes is tightly associated with the CRISPR sequences. The two most highly conserved members (cas1 and cas2, for “CRISPR associated”) are found in all cases

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#Unit 3. Fundamental Processes

The protospacer adjacent motif (or PAM for short) is a short DNA sequence (usually 2-6 base pairs in length) that follows the DNA region targeted for cleavage by the CRISPR system, such as CRISPR-Cas9. The PAM is required for a Cas nuclease to cut and is generally found 3-4 nucleotides downstream from the cut site

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#Unit 3. Fundamental Processes

cas1, cas2, and cas4 required to create protospacer sequences Cas1 is  integrase, whereas Cas2 is a ribonuclease. In contrast, of other Cas proteins, Cas6 is involved in expression and processing of the CRISPR cluster and Cas3 in the interference of viral infection.