Engineered 
transcriptional activator-like effectors (TALEs) are versatile tools for 
genome manipulation with applications in research and clinical contexts. One current drawback of TALEs is that the 5′ 
nucleotide of the target is specific for 
thymine (T). TALE domains with alternative 5′ 
nucleotide specificities could expand the scope of 
DNA target sequences that can be bound by TALEs. This disclosure provides methods and strategies for the continuous evolution of proteins comprising 
DNA-binding domains, e.g., TALE domains. In some aspects, this disclosure provides methods and strategies for evolving such proteins under 
positive selection for a desired 
DNA-binding activity and / or under 
negative selection against one or more undesired (e.g., off-target) DNA-binding activities. Some aspects of this disclosure provide engineered TALE domains and TALEs comprising such engineered domains, e.g., TALE nucleases (TALENs), TALE transcriptional activators, TALE transcriptional repressors, and TALE epigenetic modification enzymes, with altered 5′ 
nucleotide specificities of target sequences. Engineered TALEs that target ATM with greater specificity are also provided.