ProcedureGeneReplacements < Lab

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---+++ Gene replacement using pKOV vector


---++++ Before beginning part 1: design primers
   1 Insert should be ~1kb with approximately 500bp on either side of mutation, without disrupting neighboring genes. 
   1 At 5' ends of both forward and reverse primers, include 1) short CG clamp (CGC), 2) Not1 site (GCGGCCGC) on forward primer and BamH1 restriction site (GGATTC) on reverse. So each primer should look like: 5'- CGC GGA TTC (normal PCRing primer) - 3'
   
---++++Before beginning part 2: verify pKOV markers (ts, sacB, cat)
   1 Grow up overnight REL606 pKOV in LB + cam (tests camR)
   1 Dilute in saline 3x 1:100 (so 100ul in 10ml saline) and plate 100 ul on 1) LB cam @ 30 degrees, 2) LB cam @ 42 degree, and 3) LB + sucrose @ 30 degrees. Cells should grow at 30 but not at 43 or with sucrose (or at least very few colonies). 
   1 Also make a glycerol stock of the overnight culture (200µl 80% glycerol, 1ml cells) and store in -80°C
   1 ALL remaining cells from the overnight culture should be spun down at 10,000xg for 10 minutes and miniprepped. You'll need your own plasmid stock for the BamH1 digestion. 

---++++ Inoculate strain (day 0)
   1 Grow up appropriate stain with desired mutation (and WT for a control) in 5ml LB overnight

---++++ Purify genomic DNA
   1 Use Invitrogen gDNA isolation kit. Spin down all 5ml of cells and follow kit instructions. Elute with 100ul water. 

---++++ PCR out gene
   1 PCR out desired gene with primers design as described above
   1 Run gel with 5µl sample to verify PCR worked (if whole cell PCR doesn't work, gDNA extract and repeat the PCR. This should be reliable.)
   1 PCR purify rest of sample
   
---++++ Not1/BamH1 double digestion

*You'll need to digest both vector plasmid and PCR insert(s). 
  
%TABLE{dataalign="center"}%
| *Reagent* | *Final concentration* | *µl* |
| Buffer 4 | 1X | 5 |
| BamH1-HF | 50 U | 2.5 |
| Not1-HF | 50 U | 2.5 |
| BSA | 1X | 0.5 |
| DNA | >50 ng | 39.5 |
| *total* | *-* | *50* |

   1 Digest 3hr at 37°C (For the HF BamH1 you do not need to do a heat inactivation). 
   1 Store at -20°C or immediately run entire sample on gel for gel extraction.
   1 Gel extract both inserts (~1kb) and vector (the entire vector is 8.6kb, but minus the 3kb stuffer sequence that you should be cutting out, *the doubly cut vector should be 5.6kb*)
   1 Store purified DNA at -20°C or move on to AP treatment. 

---++++ Antarctic phosphatase treatment 

*This is a VECTOR ONLY step! Save your insert(s) for ligation.*

| *Reagent* | *µl* |
|cut vector | 50 |
| AP buffer | 6 |
| AP enzyme | 1 |
| water | 3 |
| *total* | *60* |

   1 Digest 15 minutes at 37°C, then 5 minutes at 65°C
   1 PCR purify the AP-treated vector 

---++++ Ligation

   1 Nanodrop both inserts and vector and record ng/ul
   1 Look up the size (in bp) of both insert and vector. You'll need both these to calculate ligation volumes because concentration is based on molarity. 
   1 Calculate insert and vector volumes (insert will be 3x the molar concentration...see the formula below)

*Insert:*    (30/3000)(size in bp) = # / (concentration in ng/ul) = *x µl of insert*

*Vector:*   (10/3000)(size in bp) = # / (concentration in ng/ul) = *y µl of vector*

*Ligation Reaction*

| *Reagent* | *µl* |
| ligation buffer | 2 |
| insert | x |
| vector | y |
| T4 ligase | 1 |
| water | up to 20 |
| *total* | *20* |

Your negative control should be (cut) vector without an insert (add more water to make 20µl).

Incubate at 16°C overnight

---++++ Transformation

   1 Thaw electrocompetent cells on ice (2 tubes for controls and 1 tube for each reaction)
   1 Put cuvettes on ice and thaw ligation product (plus negative vector-only control)
   1 Thaw uncut pKOV (this is your positive control)
   1 Add 1µl of each DNA condition to 40µl REL606 cells, flick to mix and pipette into cold cuvettes. 
   1 Add 1ml room temperature SOC into the old microfuge tubes. 
   1 Electroporate each and immediately pipette 20µl (using red tips) room temperature SOC buffer into cuvette and pipette out all liquid from cuvette into the 1.5ml microfuge tube. 
   1 Incubate tubes shaking on their sides for 2-5 hours at 30°C to recover.
   1 Pipette 100µl onto LB + cam plates and grow overnight at 30°C. 

---++++ Confirming plasmid

   1 Use primers CKO3 = 5'-AGGGCAGGGTCGTTAAATAGC-3'  and EKO33 = 5'-TTAATGCGCCGCTACAGGGCG-3' to screen camR colonies (the two are on the plasmid, it will say if there is an insert of the right size or not in the vector)
   1 PCR n°2 on 2&#956;L cultures (for clones ok with the PCR n°1) with CKO3 and the primer 1 of the first cloning step, another with CKO3 and the primer 2 of the first cloning step (CKO3 is on the plasmid, primer 1 and 2 on the insert but you don’t know what is the sense of the insert on the plasmid. It will say if there is an insert the one you are expected)
   1 If OK, make a plasmid maxiprep on 1 or 2 colonies.

---++++ Allelic exchange with suicide plasmid pKOV

   *-Permissive T° : 30°C*
   *-Restrictive T° : 43°C*
   1 Transform desired electrocompetent strain (REL606) with 3µl of suicide plasmid.
   1 Incubate for 1-2 hr at 30°C.
   1 Plate cells on LB agar + cam plates and grow overnight at 30°C.
   1 Pick 6 colonies and dilute in 200µl saline. 
   1 Dilute this 1:10, 1:100, and 1:1000 in 200µl saline. Spread 100µl of these dilutions on LB + cam plates (preheated at 43°C). *Integration of the plasmid step.*
   1 Grown these plates overnight at 43°C. 
   1 In addition, streak once directly from the 30°C plate to another 43°C LB + cam plate (reduces noise of the temperature resistant colonies). 
   1 Lastly for the integration step, save 4 transformant colonies from the LB + cam 30°C plates in 40% glycerol.
   1 Next day, pick a colony without taking satellites and dilute in 1ml saline. Dilute this another 1:10, 1:100, and 1:1000 in 200µl saline. 
   1 Plate 100µl of all dilutions (including the 1ml "undiluted") on LB + 5% w/v sucrose plates (without NaCl????). Incubate these at 30°C overnight. *Excision of the plasmid step.*
   1 Replica plating onto LB + cam plates: patch 50 to 200 colonies to LB + cam plates and grow overnight at 30°C. (If the 1:1000 plate had more than 10 colonies, something is wrong... toss these and try again). *Testing for loss of plasmid (camR)*
   1 Recover the same 50 to 200 clones in LB and 20% glycerol and store at -80°C. 
   1 Screen clone for the desired allele by PCR, digestion and Southern blot? Or PCR and sequencing. (First genomic DNA isolation if whole cell doesn't work?)



-- Main.LindseyWolf - 12 Oct 2011
This topic: Lab > WebHome > ProtocolList > ProcedureGeneReplacements
Topic revision: r9 - 2012-03-07 - LindseyWolf