tokens: After Northern blot hybridization , two Cx31 transcripts of 2 . 2 and 1 . 8 kb were detected in total RNA of the human keratinocyte cell line HaCaT and two transcripts of 2 . 2 and 1 . 9 kb in total RNA of E6 / E7 transfected human keratinocytes ( HEK cells ) .