The present invention relates to temperature-sensitive variants of a Class-II Cas9 protein, polynucleotides encoding said variants, nucleic acid constructs and expression vectors comprising polynucleotides encoding said variants, host cells expressing said variant, methods of transient repression and expression of one or more genome target sequence using said variants, and use of said variants, polynucleotides, nucleic acid constructs, expression vectors, host cells, and methods.