CRISPR-Cas systems and methods for altering expression of gene products, structural information and inducible modular Cas enzymes

A polynucleotide encoding

• i) a first Cas protein fusion construct comprising a first fragment of a Cas protein attached to a first half of an inducible dimer;
• ii) a second Cas protein fusion construct comprising a second fragment of the Cas protein attached to a second half of the inducible dimer;
• or
• iii) both the first and second Cas protein fusion constructs, the first Cas protein fusion construct comprising the first fragment of the Cas protein attached to the first half of an inducible dimer and the second Cas protein fusion construct comprising the second fragment of the Cas protein attached to the second half of the inducible dimer,
• wherein the first Cas protein fusion construct is operably linked to one or more nuclear localization signals,
• wherein the second Cas protein fusion construct is operably linked to one or more nuclear export signals,
• wherein contact with an inducer energy source brings the first and second halves of the inducible dimer together,
• wherein bringing the first and second halves of the inducible dimer together allows the first and second fragments of the Cas protein to form a complex with a guide RNA to constitute a functional CRISPR-Cas system,
• wherein the guide RNA comprises a guide sequence capable of hybridizing to a target sequence in a genomic locus of interest in a cell, and
• wherein the functional CRISPR-Cas system binds to the target sequence.