Complex sentence: During persistent infections the viral genomes often integrate into the host chromosome, causing an overexpression of the viral proteins E6 and E7, which induce immortalization and malignant transformation of cells conferring a growth advantage to the infected cells.
Split into simpler sentences: During persistent infections the viral genomes often integrate into the host chromosome, which results in an overexpression of the viral proteins E6 and E7. These oncoproteins induce immortalization and malignant transformation of cells conferring a certain growth advantage to the infected cells.