Microinjection overexpression

The evidence indicating an anti-apoptotic effect of E2F1 was first provided by the studies of E2F1 overexpression. " Microinjection of the wild type-E2Fl cDNA, but not mutated E2F1 cDNA, into quiescent cells can activate DNA synthesis and induce S-phase entry. " Further studies indicated that ovetexpression of E2F1 can cause transformation of primary cells. In contrast, mutation of E2F1 is sufficient to block cell proliferation completely." ... 

The study of lamin assembly by the microinjection of fluorescently labeled lamins has the advantage that controlled amounts of renatured protein can be injected, and that the manipulated cells can be continuously observed. The formation of heterodimeric complexes between microinjected 5-IAF-labeled lamins and the endogenous lamins can be largely excluded because the fluorescently labeled lamins are mainly in the form of homodimers assembled during dialysis. Comparison of our microinjection data with results obtained by transfection experiments demonstrates that the mutant phenotype can be obscured in transfected cells by overexpression and/or the formation of heterooligomeric complexes of mutant molecules with wild-type lamins of the transfected cells (Schmidt and Krohne, 1995). Therefore we believe that transfection experiments performed with cDNAs coding for mutated nuclear proteins should eventually be controlled by the microinjection of fluorescently labeled protein. 

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