1. A method of treating sickle cell disease or beta-thalassemia in a subject comprising administering to said subject a cell comprising an edited hemoglobin subunit gamma 1 and/or 2 (HBG1/2) promoter, wherein said edited HBG 1/2 promoter comprises an A to G alteration at position 5 and/or position 8 of the nucleotide sequence of SEQ ID NO: 177, wherein the cell is prepared by contacting the cell with a guide RNA and a base editor comprising a polynucleotide programmable DNA binding domain and an adenosine deaminase domain, wherein the adenosine deaminase domain comprises an arginine (R) or a threonine (T) at amino acid position 147 of the following amino acid sequence, wherein the adenosine deaminase has at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 2, wherein said guide RNA targets said base editor to effect a deamination of a nucleobase of the HBG1/2 promoter in the cell, thereby effecting said A to G alteration at position 5 and/or position 8 of the nucleotide sequence of SEQ ID NO: 177, wherein deamination of the nucleobase of the HBG1/2 promoter in the cell effects an increase in gamma globin (HbF) expression in the subject when administered to said subject as compared to a subject without said cell administered.