diff --git a/README.md b/README.md
new file mode 100644
index 0000000000000000000000000000000000000000..7de83e4dcd3111451f999acc49c63b862186fba4
--- /dev/null
+++ b/README.md
@@ -0,0 +1,29 @@
+This repository contains the code used in the paper:
+
+**A CRISPRi screen in E. coli reveals an unexpected sequence-specific toxicity of dCas9**
+Lun Cui, Antoine Vigouroux, Francois Rousset, Hugo Varet, Varun Khanna & David Bikard
+
+
+In this study We designed a library of 84215 unique guide RNAs targeting random positions 
+along the genome of E. coli MG1655, with the simple requirement of a “NGG” PAM. The library 
+contains an average of 19 targets per gene. A pool of guide RNAs obtained through on-chip 
+oligo synthesis was cloned under the control of a constitutive promoter on plasmid psgRNA 
+and electroporated in strain LC-E18 carrying the dCas9 gene under the control of a Ptet 
+promoter in the chromosome. The pooled library of cells was then grown in rich medium 
+over 17 generations with anhydrotetracycline (aTc). The effect of each guide on the cell fitness can be measured as 
+the fold change in abundance (log2FC) of the guide RNA in the library 
+during the course of the experiment, as measured through deep sequencing of the library.
+
+The log2FC data for all guides in the screen can be found in the file Supplementary_table_6-screen_data.csv
+
+The analysis is divded in three jupyter notebooks:
+* Effect of dCas9 binding position and orientation.ipynb
+> In this notebook we look at the effect of dCas9 binding position and orientation. In particular we perform an analysis of polar and reverse-polar effects.
+
+* off-target analysis.ipynb
+> In this notebook we investigate whether the unexpected fitness defect produced by some guides in the screen can be explained by off-target positions blocking the expression of essential or fitness genes.
+  
+* bad-seed analysis.ipynb
+> In this notebook we use a machine learning approach to reveal how dCas9 can kill _E. coli_ when guided by some specific 5nt PAM-proximal sequences 
+  
+