The present invention relates to a polynucleotide comprising (i) a sequence encoding an anti-CRISPR (Acr) polypeptide and (ii) an miRNA target sequence and to vectors and host cells related thereto. The present invention further relates to a kit comprising (I) a first polynucleotide comprising (i) a sequence encoding an anti-CRISPR (Acr) polypeptide and (ii) an RNA-interference (RNAi) target sequence; and a Cas nuclease or a second polynucleotide comprising an expressible gene encoding a Cas nuclease; (II) a first polynucleotide comprising (i) a sequence encoding an anti-CRISPR (Acr) polypeptide and (ii) an RNA-interference (RNAi) target sequence, said first polynucleotide further comprising an expressible gene encoding a first fragment of a Cas nuclease, and a second polynucleotide comprising an expressible gene encoding a second fragment of a Cas nuclease, wherein said first and second fragment of said Cas nuclease together reconstitute an active Cas nuclease; or (III) a first polynucleotide comprising (i) a sequence encoding an anti-CRISPR (Acr) polypeptide, (ii) an RNA-interference (RNAi) target sequence, and (iii) a sequence encoding a Cas nuclease; and a second polynucleotide comprising an expressible gene encoding an inhibitory RNA, preferably a siRNA or a miRNA hybridizing to said RNAi target sequence, more preferably a siRNA hybridizing to said RNAi target sequence. Further, the present invention relates to methods and uses related to the aforesaid means.