Disclosed herein are Type I Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/CRISPR-associated (Cas) system related compositions and methods of using said Type I CRISPR/Cas system related compositions for altering gene expression and genome engineering. The invention relates to compositions comprising Type I CRISPR-Cas polypeptides and CRISPR array nucleic acids designed for genome modification in eukaryotic cells and for targeted killing of eukaryotic cells.