sentences:  These findings were later added to in another extensive study, that found a third E box site.In addition, the same findings postulated that two physical entities within the gene sequence could have a role in the expression levels of human C4A and C4B, which include the both presence of the endogenous retrovirus that can have positive or negative regulatory influences affecting C4 transcription and the varying genetic environment (dependent on which genetic modular component is present) past position -1524.To provide more context, in the latter study, the previously noted bimodular structure (C4A-C4B) has been updated to a quadrimodular structure of one to four discrete segments, containing one or more RP-C4-CYP21-TNX (RCCX) modules.