CRISPR  (Clustered regularly interspaced short palindromic repeats); is a family of DNA sequences within the genomes of prokaryotic organisms such as bacteria and archaea. These sequences are derived from DNA fragments from viruses that have previously infected the prokaryote and are used to detect and destroy DNA from similar viruses during subsequent infections. Hence these sequences play a key role in the antiviral defense system of prokaryotes.
The CRISPR-Cas system is a prokaryotic immune system that confers resistance to foreign genetic elements such as those present within plasmids and phages that provides a form of acquired immunity. RNA harboring the spacer sequence helps Cas (CRISPR-associated) proteins recognize and cut foreign pathogenic DNA. Other RNA-guided Cas proteins cut foreign RNA. CRISPR are found in approximately 50% of sequenced bacterial genomes and nearly 90% of sequenced archaea.

CRISPR Associated Protein 9

Hence Cas9 (CRISPR associated protein 9) is an RNA-guided DNA endonuclease enzyme with the CRISPR; adaptive immunity system in Streptococcus pyogenes; among other bacteria. S. pyogenes utilizes Cas9 to memorize.  and later interrogate and cleave foreign DNA,  such as invading bacteriophage DNA or plasmid DNA.
Therefore the DNA substrate is complementary to the guide RNA, Cas9 cleaves the invading DNA. In this sense, the CRISPR-Cas9 mechanism has a number of parallels with the RNA interference (RNAi) mechanism in eukaryotes. Promega Corporation announced today it has signed. A non-exclusive license agreement with the Broad Institute of MIT and Harvard to sell tools and reagents for CRISPR-Cas9 gene editing; providing scientists new tools for interrogating endogenous biology.
Under the agreement, Promega will combine CRISPR-Cas9 technology; with its products that knock-in Promega genetic reporters to the genomes of any cell or cell line; enabling customers to explore endogenous biology at physiologically relevant expression levels. The combination of CRISPR-Cas9 and Promega gene reporters have proven powerful in understanding critical areas of biology.

Promega HiBiT Protein Tagging System

The Promega HiBiT Protein Tagging System can combine with CRISPR-Cas9-mediated gene editing to tag endogenous proteins; simplify their study under natural expression conditions. Another paper also in ACS Chemical Biology explains a strategy for monitoring PROTAC-mediated degradation of endogenously tagged HiBiT-BET family members in live cells.
But With this combination of CRISPR and our most advanced reporter technologies like HiBiT;  look at the dynamics of endogenous proteins in real time with unprecedented ease and sensitivity.” Promega currently offers a number of ways scientists can leverage high power reporters with CRISPR-Cas9 technology; including services to create custom assays or immediate availability of basic reporter tools for labs to configure with CRISPR gene editing.