Single adeno-associated virus (AAV)-sized nucleotide for use in CRISPR interference or activation

A nucleic acid, comprising:

• a) a nucleotide sequence encoding a Cas polypeptide that is a Cas9 polypeptide or a Cas12 polypeptide;
• b) a nucleotide sequence encoding a repressor domain or an activator domain attached to the nucleotide sequence encoding the Cas polypeptide via a nucleotide sequence encoding a first linker consisting of 6 to about 60 amino acids;
• c) a first promoter operably connected to the nucleotide sequence encoding the repressor or activator domain or the nucleotide sequence encoding the Cas polypeptide, such that the first promoter drives expression of the repressor or activator domain and the Cas polypeptide;
• d) a nucleotide sequence encoding a nuclear localization signal (NLS);
• e) a nucleotide sequence encoding a second linker, wherein the second linker is alpha-helical when the Cas polypeptide is the Cas9 polypeptide or flexible when the Cas polypeptide is the Cas12 polypeptide, and consists of about 15 to a bout 22 amino acids, wherein the second linker connects the Cas polypeptide to the NLS;
• and
• f) a second promoter operably connected to a nucleotide sequence encoding a guide RNA (gRNA).