Researchers developed a self-inactivating (SIN) lentivirus vector based on human immunodeficiency virus type 1 (HIV-1) that can transduce nondividing cells. The U3 region of the 5' long terminal repeat (LTR) was replaced with the cytomegalovirus (CMV) promoter, resulting in Tat-independent transcription but maintaining high expression levels. A SIN vector was created by deleting 133 bp in the U3 region of the 3' LTR, including the TATA box and binding sites for transcription factors Sp1 and NF-κB. This deletion is transferred to the 5' LTR after reverse transcription and integration, leading to transcriptional inactivation of the LTR in proviruses. SIN viruses maintain high titers and efficiently transduce neurons and retinal cells. The HIV-1 LTR promoter can be transcriptionally active in neurons even without Tat. SIN vectors are safer for gene therapy and have broader applicability for gene transfer in nondividing cells. The study also shows that SIN vectors can transduce a wider range of retinal cells compared to wild-type vectors, suggesting that the HIV-1 LTR may negatively influence the internal CMV promoter in some cell types. The SIN HIV vectors are safer and more effective for gene therapy due to their reduced risk of replication-competent virus generation and enhanced safety features. The study highlights the potential of SIN vectors for efficient and safe gene transfer in nondividing cells.Researchers developed a self-inactivating (SIN) lentivirus vector based on human immunodeficiency virus type 1 (HIV-1) that can transduce nondividing cells. The U3 region of the 5' long terminal repeat (LTR) was replaced with the cytomegalovirus (CMV) promoter, resulting in Tat-independent transcription but maintaining high expression levels. A SIN vector was created by deleting 133 bp in the U3 region of the 3' LTR, including the TATA box and binding sites for transcription factors Sp1 and NF-κB. This deletion is transferred to the 5' LTR after reverse transcription and integration, leading to transcriptional inactivation of the LTR in proviruses. SIN viruses maintain high titers and efficiently transduce neurons and retinal cells. The HIV-1 LTR promoter can be transcriptionally active in neurons even without Tat. SIN vectors are safer for gene therapy and have broader applicability for gene transfer in nondividing cells. The study also shows that SIN vectors can transduce a wider range of retinal cells compared to wild-type vectors, suggesting that the HIV-1 LTR may negatively influence the internal CMV promoter in some cell types. The SIN HIV vectors are safer and more effective for gene therapy due to their reduced risk of replication-competent virus generation and enhanced safety features. The study highlights the potential of SIN vectors for efficient and safe gene transfer in nondividing cells.